Question

Why is gene repression of a eukaryotic gene by a noncoding RNA possibly more efficient than repression by a protein repressor?

Answer 1

Gene repression by a protein repressor which is a DNA- or RNA- binding protein inhibits the expression of the associated DNA- or RNA- by binding to the operator/promoter or mRNA.

Gene repression by the protein is required for cellular differentiation in tissue specific manner. For example, Red blood cells that carry oxygen to different cells, muscular cells contraction and expansion and many more. Thus the proteins that acts as transcription factors have highly conserved sequences and are affected by the type of activator/repressor and signal of the cell to either switch it on or off.

Besides normal gene expression, there are many more genes that are not expressed or are repressed from their expression. Such mechanisms are the result of non-coding RNA: small inhibitory RNA (siRNA) and microRNA (miRNA).

Both siRNA and miRNA are small RNA molecules that have different mechanisms for inhibiting translation in association with a ribonucleoprotein complex called RNA induced silencing complex (RISC) that binds to mRNA and their degradation.

Gene repression by non-coding RNA is more informative than protein repressors:

· miRNA have given information on phenotypic changes in an organism due to the evolutionary changes in gene-regulatory network of cell differentiation

· Anti-viral defense of siRNA has been shown in certain plants and animal species, which can be used for understanding anti-viral defense mechanism and drug development

· Non-coding RNA can be used to study the role of specific proteins in a cell where shutting off the expression of protein coding gene will deduce the effects of protein deficiency.

· Studies using non-coding RNA could lead to development of drugs for different plant, human and animal diseases.