1A.After entry, what is the first process labeled “A”? 1B. Which protein complex

Question

1A.After entry, what is the first process labeled “A”?

1B. Which protein complex is doing the process shown in “A”?

1C.Why can this happen as soon as the genome enters the cell?

2. Over on the upper right side of the figure, labeled “B”, why does the virus shut off host cell translation and transcription? What is the benefit of this to the virus?

3. What viral process is happening part C and what enzyme does this?

4. What are the blue lines made in part D and what is the dual purpose of these blue lines?

Pro-apoptotic Anti-apoptotic Shut off host cell Sta 0 host cell (cap Polyprotein Interactions between the vius and the cel cycle ral replication complex dsRNA (atency?) strand (goniome 3 3 3 Cell lysis Veal ogrees Nature Reviews Microbiology 3, 765-776 (October 2005) I dol:10.1038/nrmicro1284

Explanation / Answer

1 A. After the virus enters the cell, the first process that takes place is the translation. this is because the positive-stranded RNA is capable of serving both as genomic and mRNA for the virus.

B. The process that is initiated in A is translation which is initiated by a protein present in the genome of the virus. Though the genome lacks 5' cap it can be recognized by the ribosomes of the host machinery and the synthesis of proteins start. The process gets initiated by an IRES that is Internal Ribosome Entry Site using the host cell ribosomes.

C. This happens immediately after the viral entry because the genome of the virus is cable to synthesize its own proteins. This is necessary for the virus to synthesize the other necessary protines to infect the other cells and to make a copy of itself. The RNA strand of the virus is similar to the mammalian RNA except for 5' cap but the IRES site makes it possible and the process starts as soon as it enters the cell.

2. The viral genome shuts off the host machinery for its own benefit and can carry out its replication easily. This happens because the host machinery is 5' cap dependent, as a result, it gets inhibited and the viral protein synthesis occurs. This shutting down of the translation and transcription of the host cells results in the coding of the viral proteins that are necessary for the replication of the viral genome. This is beneficial to the virus as the host machinery is left with the viral genes to function and as a result, the virus is capable of replicating itself into a number of copies.

3. The replication of the genome is taking place. This happens with the help of DNA polymerase of the host cell machinery. +ve ssRNA gets converted to -ve ssRNA which in turns gets converted to +ve ssRNA with the help of DNA polymerase. Then the sense strand is transcribed to produce the necessary proteins and enzymes for the regulation of their transcription and replication.

4. These blue lines in D are the newly synthesized +ss RNA strands which will go for the packaging of the new virus cells. These lines serve two purposes: one gets its packaged into the new virus and second, it can enter the whole process again to produce new +ss RNA strands.

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