Virus Updates

Feeling a bit guilty here because I have yet to put up the updates on virus as promised and I could not find the correction sheet which I have typed out earlier *groan :(. But no worry, my retentive memory is somewhat still working :) - though I wish to be back in my classrooms talking about this interesting topic ....oh well.. at least I substituted it with a lecture here in Cambridge on bacteria to our Bio students here :P

Anyway here goes:

1) matrix proteins - what are they? Are they important?

From Wiki: In virology, matrix proteins are structural proteins linking the viral envelope with the virus core.

This protein is noted in both influenza and HIV but their implications are different. In influenza, the matrix protein M1 as seen in the given diagram IS also the capsid protein so there is only one level of protein layer enclosing the nucleoprotein. On the other handd, for HIV, the capsid protein and matrix protein genome. The matrix protein is really there to hold the gp41 to the membrane but that doesnt really matter. What you should note is that for HIV, therefore, there are two layers of protein enclosing the genome.

2) Is polypeptide = polyprotein?

They are two different things.
Polypeptide will fold to form one protein.
A polyprotein refer to polypeptide that can be cut into several pieces, each of which can be folded into various structural or enzymatic proteins. In the case of HIV for example, the gag gene encodes for the capsid and matrix protein while the pol gene encodes for the viral protease, RT and integrase. what do you think env gene encodes?

2a) what is this splicing business?
Due to alternative splicing, sometimes you get mRNA of either gag, gag-pol or just env.

3)If you have not made this change in your notes already, pls do. Page 19. Bullet 5/6. a double-stranded DNA is not a provirus. a provirus only exists when it is integrated into the host's genome. Just as we called the integrate phage genome in a lysogenic cycle a prophage.

4) Qn: How do you get a double-stranded DNA in HIV? Who is involved?

5) Your covering tutor should have covered with you on: influenza is a -ve sense RNA virus (-ve sense RNA implies that the genome cannot be used as mRNA directly and has to be converted to the +ve sense (mRNA) before translation can take place) thus the template used to make the new genome and proteins should be the +ve sense mRNA that is transcribed from the -ve sense genome... If not, I will talk about it again next time.

That's all I have I believe =)
Have fun!