Index >>Viruses and Cancer >>Protein Synthesis

Protein Synthesis - The RNA transcribed before DNA replication is called early RNA, and that made after replication is called late RNA.
Polyoma and SV40 viruses specify small amounts of RNA in permissive hosts within 12 hours after infection (early RNA).
From 12-18 hours after viral replication begins, about x 100 more RNA is transcribed (late RNA).
Early RNA has complementary sequences to only one of the two DNA strands.
This strand is called the E strand. Late RNA has complementary sequences to only the other strand (L strand).
It thus appears that a strand switch occurs in DNA transcription in both viruses.

The amino acid sequence of VP3 IS contained within the -CooH two ,thirds of VP2.
The sequences coding for VP2 and VP1 overlap by about a hundred nucleotides.
It will thus be seen that all the three mRMAs contain sequences for coding VPI, but only 16SR mRNA synthesizes VP1 actively.
Similarly, 19S mRNA contains the sequences for coding VP3 but does not do so.
This phenomenon has been explained by assuming that 19S and 18S mRNAs contain cryptic initiation sites which are inactive.
Post transcription polyadenylation (addition of poly(A) sequence) Occurs at the 3 end of mRNA.
The poly(A) sequence is not coded by viral RNA.
The 5 triphosphate end is capped with 7-methyl guanosine