Question

Define RNA-based mechanisms in simple language.

Answer 1

RNA-based mechanisms:

The three main types of RNA are - mRNA, rRNA, and tRNA.

Roles:

mRNA: Genes are copied to codons on mRNA which are then used by ribosomes to make proteins.

rRNA: rRNA is essential in making ribosomes.

tRNA: These types of RNAs are used to transfer amino acids to translation machinery on ribosomes to build proteins.

RNA-Based Mechanisms:

There is evidence that noncoding RNAs and the RNA interference machinery are fundamental determinants of chromatin-based gene expression.

In mammalian systems, the role of XIST RNA in X chromosome inactivation, Air RNA at the murine imprinted Igf2r locus, and these examples importantly involve coordinated epigenetic activities including DNA methylation and histone posttranslational modifications.

In contrast, micro-RNAs and short interfering (si)RNAs, ? 21 to 26 nucleotide small RNA species, are well-known mediators of cytoplasmic, posttranscriptional gene silencing as components of the RNA-induced silencing complex (RISC).

Micro-RNAs are derived from nuclear transcripts with characteristic stem–loop structures and transported to the cytoplasm.

Alternatively, siRNAs are derived from long double-stranded RNA precursors delivered exogenously to cells or that arise naturally within cells.

Exogenously administered siRNAs directed at promoter regions can effectuate transcriptional gene silencing in mammalian cells by inducing site-specific DNA methylation and repressive histone posttranslational modifications.

Given that at least 15% to 20% of mouse and human genes, respectively, demonstrate cis-encoded natural antisense transcripts, it is anticipated that RNA-based mechanisms will have far-reaching influence in the regulation of mammalian gene expression.