ANTISENSE RNA

BY SREEREMYA.SM.phil

INTRODUCTION Antisense RNA (asRNA) is a single-

stranded RNA that is complementary to a messenger RNA (mRNA) strand transcribed within a cell. Some authors have used the term micRNA (mRNA-interfering complementary RNA) to refer to these RNAs but it is not widely used

Antisense RNA may be introduced into a cell to inhibit translation of a complementary mRNA by base pairing to it and physically obstructing the translation machinery

PROCSS . An example of naturally occurring

mRNA antisense mechanism is the hok/sok system of the E. coli R1 plasmid.

Antisense RNA has long been thought of as a promising technique for disease therapy; the only such case to have reached the market is the drug fomivirsen.

One commentator has characterized antisense RNA as one of "dozens of technologies that are gorgeous in concept, but exasperating in [commercialization]"

CONT….. Generally, antisense RNA still lack

effective design, biological activity, and efficient route of administration.

Historically, the effects of antisense RNA have often been confused with the effects of RNA interference (RNAi), a related process in which double-stranded RNA fragments called small interfering RNAs trigger catalytically mediated gene silencing, most typically by targeting the RNA-induced silencing complex (RISC) to bind to and degrade the mRNA.

CONT….. Attempts to genetically engineer

transgenic plants to express antisense RNA instead activate the RNAi pathway, although the processes result in differing magnitudes of the same downstream effect, gene silencing.

Well-known examples include the Flavr Savr tomato and two cultivars of ringspot-resistant papaya.

CONT…… Transcription of longer cis-antisense transcripts

is a common phenomenon in the mammalian transcriptome

Although the function of some cases have been described, such as the Zeb2/Sip1 antisense RNA, no general function has been elucidated. In the case of Zeb2/Sip1, the antisense noncoding RNA is opposite the 5' splice site of an intron in the 5'UTR of the Zeb2 mRNA. Expression of the antisense ncRNA prevents splicing of an intron that contains a ribosome entry site necessary for efficient expression of the Zeb2 protein.

CONT…. Transcriptional gene silencing is the

result of histone modifications, creating an environment of heterochromatin around a gene that makes it inaccessible to transcriptional machinery (RNA polymerase, transcription factors, etc.).

CONT….. Transcription of long antisense ncRNAs

is often concordant with the associated protein-coding gene, but more detailed studies have revealed that the relative expression patterns of the mRNA and antisense ncRNA are complex.

CONT….. Transcriptional Gene Silencing: Genomic Imprinting Paramutation Transposon silencing Transgene silencing Transcriptional gene silencing

CONCLUSION Thus antisense RNA can be majourly

used in major molecular analysis To inhibit the cell translation an

antisense RNA has a pivotal role to play Since antisense RNA produces

complementary strand to mRNA it is used in specific inhibition process

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