Biogenesis and Function of miRNAs and Their Role in Cancer
Yustina Nuke Ardiyan1, Johana Puspasari Dwi Pratiwi2
Universitas Kristen Duta Wacana, Indonesia
|
Keywords |
Abstract |
|
Small
RNA,
miRNA, mRNA, cancer |
MicroRNA (miRNA) is a
small RNA molecule that regulates post-transcriptional gene expression. miRNA
combines with the RNA-induced silencing complex (RISC) and carries out its
function in controlling translation. The formation of miRNA involves enzymes
and proteins that cut it in its processing as well as protein complexes in
the cytoplasm that make the miRNA mature. Several changes, for example
deletion or overexpression, can occur in miRNAs, causing cancer growth. The
aim of this study was to investigate the process of miRNA biogenesis as well
as analyze how changes in miRNA expression can
affect the biological pathways involved in cancer. This type of research is a
literature review. The data that has been collected is then analyzed in three stages, namely data reduction, data
presentation and drawing conclusions. The results show that the role of
miRNAs is in the post-transcriptional regulation of genes. MiRNAs associate
with the RISC complex and interact with mRNA through complementary base
pairing thereby halting translation and promoting mRNA degradation. MiRNAs
are deregulated in cancer, including over-expression of oncogenic miRNAs or
deletion of miRNA characteristics as tumor inhibitors. The results of this research also
provide a foundation for further education and advanced research in the field
of molecular biology, particularly in genetic regulation and disease
mechanisms. |
Corresponding Author: Yustina Nuke Ardiyan
E-mail: [email protected]
INTRODUCTION
There are various classes of small endogenous RNA molecules, including
tRNA, rRNA, snoRNA, miRNA, and siRNA (Pangarsa et al., 2023)
. tRNA and rRNA
function in the translation process. snoRNA plays a role in rRNA modification.
miRNAs and siRNAs are biochemically and functionally indistinguishable. Both
have 19-20 base pairs of nucleotides and combine with RISC to stop gene
expression (Kumar et al. 2019) .
miRNAs are small RNA molecules that
regulate gene expression by base pairing with certain mRNAs and reducing their
stability and translation into proteins. In humans, miRNAs are thought to
regulate the expression of at least one third of the genes encoding proteins (Alberts et al .,
2014) .
Many studies have studied and discovered hundreds of types of miRNA and their
role in cell metabolism and even in the incidence of cancer (Suryani, 2020) .
MicroRNA
(miRNA) is a small RNA molecule that plays a role in posttranscriptional
regulation of gene expression. miRNAs bind to the RNA-induced silencing complex
(RISC) to inhibit or reduce the mRNA translation process. The formation of
miRNA involves a processing process in which enzymes and proteins such as
Drosha, DGCR8, and Dicer play an important role in cutting the miRNA precursor
into a mature form that is ready to function. In the cytoplasm, mature miRNAs
combine with a protein complex within the miRISC,
which includes Ago2, TRBP, and PACT, to target specific mRNAs and control gene
expression.
Changes in miRNA expression, such as deletion or overexpression, can
have a significant impact on genetic regulation and biological mechanisms. In
the context of cancer, these changes may lead to dysfunction in the regulation
of certain genes related to cell growth and metastatic processes. For example,
certain miRNAs that normally act as tumor suppressors
may experience reduced expression, while miRNAs that act as oncogenes may
experience increased expression.
Many studies have
studied and discovered hundreds of types of miRNA and their role in cell
metabolism and even in the incidence of cancer (Suryani, 2020). Previous
research by (McFarlane & Murphy, 2010) showed that the regulatory function
of microRNAs is achieved through the RNA-induced silencing complex (RISC).
MicroRNAs assemble into RISC, activating the complex to target the messenger
RNA (mRNA) specified by the microRNA. Various models of RISC assembly have been
proposed and research continues to explore the mechanisms of RISC loading and
activation.
The degree and
nature of complementarity between the microRNA and the target determines the
mechanism of gene silencing, slicer-dependent mRNA degradation, or
slicer-independent translational inhibition. Recent evidence suggests that
P-bodies are essential for microRNA-mediated gene silencing and that RISC
assembly and silencing occurs primarily within P-bodies. The P-body model
describes microRNA sorting and switching between specialized P-body
compartments housing enzymes required for slicer-dependent and
slicer-independent silencing, addressing the reversibility of this silencing
mechanism. Detailed knowledge of microRNA pathways is essential to understand
their physiological roles and the implications associated with dysfunction and
dysregulation.
The results of this
study provide a strong foundation for further education and advanced research
in the field of molecular biology, especially related to genetic regulation and
disease mechanisms. A deeper understanding of the biogenesis and function of
miRNAs and their role in cancer provides valuable insights for scientists and
educators in elucidating the complexity of the biological pathways involved in
disease progression. These findings not only support the development of novel
miRNA-based therapies, but also stimulate further exploration of the possible
applications of genetic technology in specific and precision medicine. The aim
of this study was to investigate the process of miRNA biogenesis as well as
analyze how changes in miRNA expression can affect the biological pathways
involved in cancer.
RESEARCH
METHODS
This type of study is Literature Review. Keywords used to look for
source articles namely �small RNA�, �miRNA�, �mRNA�, and �cancer�. Search
article searched for from Google Scholar. Year article taken is from 2010 to
2023. Study conducted is with a narrative review. This research was carried out
in 2023 for 4 days. The data that has been collected is then analyzed in three stages, namely data reduction, data
presentation and drawing conclusions.
RESULTS AND
DISCUSSION
����������� Based on the results
of the literature search, 22,661 articles were found. By using keywords such as
�small RNA�, �miRNA�, �mRNA�, and �cancer�. researchers can access thousands of
scientific articles related to this topic. This search will yield a list of
articles covering various aspects of miRNA biogenesis, their function in
genetic regulation, and their critical role in various types of cancer. From
these search results, researchers can then identify the most relevant and
high-quality articles to serve as the main data source in their research. By
collecting and analyzing data from around 20 of the most relevant and trusted
articles, researchers can build a solid foundation of knowledge to support
research objectives.
Biogenesis
of miRNAs
������������� The process of forming miRNA after
transcription consists of two steps, namely cutting in the nucleus and
cytoplasm respectively, which is carried out by ribonuclease III endonuclease,
namely Drosha and Dicer. The miRNA gene is transcribed into primary miRNA (pri-miRNA) then processed
again into precursor miRNA (pre-miRNA), then miRNA duplex. miRNA will combine with RISC to become miRISC which can
carry out the function of controlling gene expression (Kurozumi et al. ,
2016) .
Figure 1. Nuclear and cytoplasmic components in the
formation of miRNA (source: Macfarlane and
Murphy, 2010)
������������� The
DNA sequence that will be transcribed as miRNA is found in the intergenic
region and intron of a gene (coding intron).
Previously, these areas were called ' junk
DNA' because their function was not yet known. miRNA precursors are less
commonly found in exons. miRNAs originating from intergenic areas are
transcribed by RNA polymerase II or III to produce pri-miRNA molecules (Bryson, 2021) .
Pri-miRNA is processed into pre-miRNA by a
microprocessor complex consisting of DGCR8 and Drosha. Pre-miRNA is carried
out of the nucleus into the cytoplasm by nucleocytoplasmic transporter
proteins, namely Exportin 5 and Ran-GTP. (Paisal & Kusmardi,
2023) .
miRNAs contained in introns are transcribed by RNA polymerase II. After
pre-mRNA is formed, splicing of
introns occurs. One hypothesis states that after splicing pri-miRNA is produced, which is then cut by Drosha and
DGCR8 to become pre-miRNA. Another hypothesis states that as a result of splicing, mirtron is formed, namely a
miRNA molecule that does not undergo microprocessor
cleavage and is directly transported outside the nucleus. Another
hypothesis states that pre-miRNA is directly produced from pre-mRNA via microprocessor cleavage.
In the cytoplasm, the pre-miRNA is
cleaved by Dicer to produce a duplex miRNA.
miRNA can also be cleaved by Ago2 to produce Ago2-cleaved precursor miRNA (ac-pre-miRNA) which then becomes a
substrate for Dicer (Angelina &
Kodariah, 2016) .
miRNA duplex releases mature miRNA to
combine with RISC to become miRISC (Angelina &
Kodariah, 2016) .
The protein complex in miRISC is Ago2, TRBP, PACT, and Dicer.
miRNAs, which were initially thought to
originate from �junk DNA� or non-coding regions of the genome, are now
recognized as key components in the post-transcriptional regulation of genes.
The discovery that the DNA sequences that produce miRNAs are found in
intergenic regions and introns of a gene (coding introns) illustrates the importance
of these regions in complex genetic regulation. The process of miRNA biogenesis begins with transcription by
RNA polymerase II or III, depending on its genomic location. MiRNA produced
from intergenic regions will be transcribed into pri-miRNA, which is then
processed into pre-miRNA by a microprocessor complex involving DGCR8 and
Drosha. Pre-miRNA is then transported from the nucleus to the cytoplasm by the
Exportin 5 and Ran-GTP complex.
Meanwhile, miRNA originating from
introns is transcribed together with pre-mRNA, and after the intron splicing
process, can produce pre-miRNA. There are several hypotheses regarding this
process, including the formation of mirtrons which are miRNAs that do not
require processing by the microprocessor complex and can be directly exported
from the nucleus. In
the cytoplasm, pre-miRNA or pre-miRNA is cleaved by the Dicer enzyme into
duplex miRNA. This process is important because mature miRNAs will be
integrated into the RISC complex (RNA-induced silencing complex), which
consists of proteins such as Ago2, TRBP, PACT, and Dicer. The RISC complex
mediates the functional effects of miRNAs by targeting complementary mRNAs,
terminating mRNA translation, or directing mRNA degradation.
miRNAs
as post-transcriptional regulators
����������� miRNAs play important
roles in many biological pathways in mammals and multicellular organisms (Mulyandarini, Rahman,
& Adelina, 2022) .
MiRNAs influence cancer-related processes such as proliferation, cell cycle
control, apoptosis, differentiation, migration, and metabolism. One miRNA
molecule can target multiple mRNAs. Mature miRNA induces posttranscriptional gene silencing along with RISC (Salinah & Wuyung,
2019) .
Figure 2. miRNAs target complementary mRNA molecules for
destruction
(source: Alberts et al, 2012)
������������� miRISC
will look for mRNA that has a nucleotide sequence that is complementary to the
miRNA it binds to. If the complementary region is very long, the mRNA will
quickly be degraded by the nucleases in miRISC. If the complementary region is
short, translation stops and the mRNA is transported to an area in the cytoplasm
where other cellular nucleases destroy it. The mRNA molecule has a short
half-life in the cytoplasm, therefore if there is no translation the poly A
tail at the 3' end continues to shorten making the mRNA unstable and ultimately
degraded (Alberts et al. ,
2014) .
MiRNAs are known to influence various
important aspects of genetic regulation, such as cell proliferation, cell cycle
control, apoptosis, cell differentiation, cell migration, and metabolism. The
ability of a single miRNA molecule to target multiple mRNAs indicates the
significant complexity of genetic regulation governed by miRNAs. The process of miRNA biogenesis, in
which mature miRNA induces posttranscriptional gene silencing via the RISC
complex, also illustrates the fundamental mechanism of how miRNAs influence
gene expression. MiRISC functions to search for mRNA that has a nucleotide
sequence that is complementary to the miRNA it binds to. When the complementary
region is long enough, the mRNA can be rapidly degraded by nucleases in miRISC,
whereas if the complementary region is short, translation of the mRNA stops and
the mRNA can be transported to other cytoplasmic regions for further
degradation.
The
role of miRNAs in cancer development
miRNAs can function as tumor
suppressors or as oncogenic factors. MiRNA dysregulation is demonstrated in
many cancer events. Deletion of miRNA genes as tumor suppressors and amplification
of miRNAs as oncogenic factors play a role in the development of cancer (Wang and Luo, 2015) .
Figure 3. Deregulation of miRNA gene transcription in cancer
through genetic,
epigenetic and transcriptional mechanisms
(source: Jansson and Lund,
2012)
miRNAs can be deregulated in cancer
development. Demethylation causes genes that are not normally expressed to
become expressed. As a result, miRNAs are upregulated and are oncogenic. miRNA
will suppress the expression of tumor
suppressor genes so that cancer develops. Downregulation of miRNAs which
causes low miRNA expression is caused by gene deletion, loss of histone
acetylation, DNA hypermethylation, suppression by oncogenic transcription
factors (e.g. Myc), and loss of the p53 transcription factor (Peng and Croce, 2016) .
Figure 4. Multiple defects in miRNA processing and escape of
mRNA
from miRNA regulation
(source: Jansson and Lund,
2012)
������������� Several
mutations or deletions in genes that play a role in miRNA processing can cause
the miRNA to not be expressed or have reduced function (Anwar, Haryono,
Aryandono, & Haryana, 2018) .
These disorders include deletion of the Drosha, p53, and Dicer genes. Mutations
can occur in the p53, XPO5, and TRBP genes. Apart from mutations or deletions,
mRNA can also escape miRNA regulation. The target sequence in mRNA can change
due to somatic translocation, alternative
splicing, or mutation. The presence of RNA
binding protein (RBP) and competitive
endogenous RNA (ceRNA) means that the miRNA cannot attach to the target
mRNA and ultimately the regulation of the miRNA cannot take place (Kamali et al., 2024).
Oncogenic
and tumor suppressive miRNAs in breast cancer
miR-21 is a type of oncogenic miRNA. In
breast cancer, miR-21 is overexpressed and suppresses tumor suppressor genes. Several studies confirmed that miR-21 is
associated with cancer clinical stage, metastasis, and poor prognosis (Harahap, 2019) .
The target genes of miR-21 include tumor
suppressor tropomyosin 1 (TPM1), programmed
cell death 4 (PDCD4), TIMP
metallopeptidase inhibitor 3 (TIMP3), and phosphatase & tensin homolog (PTEN) (Wang and Luo, 2015) .
������������� TPM1
is an actin-binding protein involved in the regulation of tethering-independent
growth and microfilament organization. miR-21 suppresses TPM1 resulting in
changes in cytoskeleton structure that lead to neoplastic development, cell
invasion, and metastasis. PDCD4 is a protein associated with apoptosis and
regulation of urokinase receptor (uPAR) which is involved in extracellular
matrix degradation. Suppression of PDCD4 causes progression to cancer (O�Bryan et al., 2017). TIMP3 is a gene
that encodes a matrix metalloproteinase
inhibitor protein. Metalloproteinases are a class of peptidases that cause
degradation of the extracellular matrix. Suppression of miR-21 causes cancer
metastasis to occur. PTEN works together with phosphoinositide 3 kinase (PI3K) in balancing levels of phosphatidylinositol phosphate 3 (PIP3)
which controls the Akt pathway. PTEN dephosphorylates PIP3 and PI3K
phosphorylates PIP2 to maintain PIP3 balance. Suppression of PTEN by miR-21
increases PIP3 accumulation resulting in excessive stimulation of the Akt
pathway, resulting in continuous growth (Wang & Luo, 2015).
Let-7
family
Let-7 is a miRNA that suppresses tumors (Angelina &
Kodariah, 2016) .
In cancer, let-7 is deleted. The targets of let-7 are the Ras oncogene and high mobility group AT-hook 2 (HMGA2).
Ras is a GTPase in signal transduction that transmits signals from outside the
cell to inside the cell to influence proliferation, growth, cytoskeleton
organization, cell movement, and survival. HMGA2 is a nonhistone transcription
factor that changes DNA conformation into an active state and is ready to be
transcribed for growth, differentiation, proliferation and survival. Let-7
deletion causes Ras and HMGA2 to become uncontrolled and leads to the
development of cancer (Wang and Luo, 2015)
CONCLUSION
miRNAs role in
post gene regulation transcription. miRNAs join with RISC and Work with method
pair base with complementary mRNA so that translation stopped and induce mRNA degradation.
miRNAs experience deregulation on cancer among other things, you can happen
excess expression miRNAs oncogenic or deletion characteristic miRNAstumor suppressor.�
REFERENCES
Alberts, Bruce, Bray, Dennis, Hopkin, Karen, Johnson,
Alexander, Lewis, Julian, Raff, Martin, Roberts, Keith, & Walter, Peter.
(2014). Essential Cell Biology (Forth Edit). New York: Garland Science.
Angelina, Aina, & Kodariah, Ria. (2016). Gene Regulatory
Molecules "microRNA": Role in Carcinogenesis and Potential as Markers
of Malignancy. Pratista Pathology , 5 (1), 52�58.
Anwar, Sumadi Lukman, Haryono, Samuel J., Aryandono, Teguh,
& Haryana, Sofia Mubarika. (2018). microRNA: biogenesis, function and
role in the process of carcinogenesis and cancer management . UGM PRESS.
Bryson, Bill. (2021). The Body: A Guide for Inhabitants .
Gramedia Pustaka Utama.
Please, Wirsma Arif. (2019). The role of microRNA in the
diagnosis and management of breast cancer. Andalas Medical Magazine , 42
(3S), 85�94.'
Kamali, M. J., Salehi, M., Mostafavi, M.,
Morovatshoar, R., Akbari, M., Latifi, N., ... & Daraei, A. (2024).
Hijacking and rewiring of host CircRNA/miRNA/mRNA competitive endogenous RNA
(ceRNA) regulatory networks by oncoviruses during development of viral
cancers. Reviews in medical virology, 34(2), e2530.
Kumar, Vinay, Frcpath, Mbbs MD, Abbas, Abul K., & Aster,
Jon C. (2019). Robbins Textbook of Pathology-E-Book . Elsevier
(Singapore) Pte Limited.
Kurozumi, Sasagu, Yamaguchi, Yuri, Kurosumi, Masafumi, Ohira,
Miki, & Matsumoto, Hiroshi. (2016). Recent trends in microRNA research
into breast cancer with particular focus on the associations between microRNAs
and intrinsic subtypes . 62 (1), 15�24.
https://doi.org/10.1038/jhg.2016.89
Mulyandarini, Hesty, Rahman, Nur, & Adelina, Rany.
(2022). Literature Study Of Fiber, Calcium, And Mirna In Colorectal Cancer:
Literature Review of Fiber, Calcium, and MiRNA in Colorectal Cancer. Journal
of Food, Health and Nutrition, Binawan University , 2 (2), 12�23.
Paisal, Paisal, & Kusmardi, Kusmardi. (2023). The Role of
Immunohistochemical Techniques in Human Testicular Biopsy Studies. Pratista
Pathology , 8 (2).
Pangarsa, Eko Adhi, Suharti, Catharina, & Haryana, Sofia
Mubarika. (2023). The Effect Of Carbogen And Nicotinamide On Biomarkers Of
Hypoxia, Angiogenesis And Tumor Volume In Non-Hodgkin Diffuse Large B-Cell
Malignant Lymphoma . Diponegoro University.
Peng, Yong, & Croce, Carlo M. (2016). The role of
MicroRNAs in human cancer . (November 2015).
https://doi.org/10.1038/sigtrans.2015.4
Salinah, Salinah, & Wuyung, Puspita Eka. (2019). The role
of miRNA-200 in the stages of cancer metastasis. Journal of Medicine and
Health: Scientific Publication, Faculty of Medicine, Sriwijaya University ,
6 (1), 37�45.
Suryani, Yani. (2020). Breast cancer . PT. Freeline
Cipta Granesia.
Wang, Wei, & Luo, Yun ping. (2015). MicroRNAs in
breast cancer : oncogenes and tumor
suppressors with clinical potential * . 16 (1),
18�31. https://doi.org/10.1631/jzus.B1400184