Paramyxovirus P gene expression
n.panjwani at lshtm.ac.uk
Tue Jun 13 09:36:18 EST 1995
I was reading about parainfluenza virus (The Biology of Parainfluenza
viruses, Clin. Microbiol. Rev., 1994, 7(2)), and one aspect of it's
molecular biology left me confused. I wonder if someone can sort it
The P gene is multicistronic. Paramyxoviruses can be divided into 2
groups based on how the P gene is expressed. PIV1 and PIV3 express the
500-600 aa product from continuous open reading frames in the P
gene transcript. Then another protein - C - is expressed from a discrete
frame within the multicistronic transcript.
PIV2 & 4 have a different gene expression pattern. Here more than one
species of transcript (mRNA) is generated by non-template dependent
insertion of two G nucleotides at a specific point in the P gene.
You therefore now have two possible P protein, and I find it impossible
to see how an activity such as that which is ascribed to P protein can
be preserved despite this kind of frameshift....
In the PIV2/4 expression strategy, a V protein is expressed from
the P gene, but directly from the positive sense genome and not from
transcribed -ve sense mRNA. Now, is this to say that in the other
members of the family have the C protein expressed, and these 2 types
and their related animal viruses have the V protein expressed.
This is inconsistent with the fact that the C protein has a highly
conserved cys-rich region that appears to a nucleic acid binding
domain. How can one group express a different protein that completely
lacks an activity that seems so crucial..
University of London
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