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GENE SILENCING PTGS or RNAi :The new star of molecular biology by Ramish waheed 6043


GENE SILENCING It is a general term describing epigenetic processes of gene regulation. It is used to describe the “switching off” of a gene by a mechanism other than genetic mutation. Genes are regulated by transcriptional or post-transcriptional level.


GENE SILENCING ( Types ) TRANSCRIPTIONAL GENE SILENCING . The result of histone modifications ,creating an environment of hitrochromatin around a gene that makes it inaccessible to transcriptional machinery (RNA polymerase ,transcription factors ,etc). POST-TRANSCRIPTIONAL GENE SILENCING (PTGS) . It is the result of mRNA of a particular gene being destroyed. The destruction of the mRNA prevents translation to form an active gene product (in most cases ,a protein).

About PTGS:

About PTGS PTGS was first described in transgenic Petunia and was named as “co-suppressor of gene expression” (The molecular mechanism remained unknown). Later plant virologists made similar observations ,and called it “Virus induced gene silencing” (VIGS). Also named transgene silencing. PTGS is now known as RNAi.


RNA INTERFERENCE (RNAi) 1998:A. Fire & C. Mello (Stanford) and U.Mass (Worcester) coined term RNAi after experiment on Caenorhabditis elegans a nematode . 1990: Plant scientists in USA&NETERLANDS (Napoli et al.,) in petunia .

How RNAi works:

How RNAi works

RNAi Machinery:

RNAi Machinery

Applications of RNAi:

Applications of RNAi Gene knockdown: Repressing a gene from being expressed allows for testing of the protein and its role in life of a cell or a larger organism. Medicinal role: dsRNAs that trigger RNAi may be usable as drugs. Also in repression of essential genes in eukaryotic human pathogens or viruses that are dissimilar from any human genes.


ACKNOWLEDGMENTS It is my fond privilege that I had the able guidance of our faculties at AIB namely Dr Grover and Dr V. Mishra with out whose teaching and guidance this presentation was not possible. I am also thankful to my friends for their valuable inputs. Last but not the least to Dr Sumeda for being tolerant and patient in the whole process. Ramish Waheed

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