Can any body help me explain whether the following statement is true or false? If the site of transcript cleavage and polyadenylation of a particular RNA in one cell is downstream of the same site used for cleavage of polyadenylation of the same RNA in a second cell, the protein produced from the longer polyadenylated RNA in the first cell will necessarily contain additional amino acids at its C-terminus.
If both RNAs are the same sequence, except one has a longer 3'UTR, then the protein products will be the same size -translation will end at the stop codon, regardless of how much more downstream RNA there is. However, if one RNA has a different 3'UTR, it is possible that splicing may be different between the two RNAs and the longer RNA may have a different stop codon, which produces a longer protein. You need to look at the full length cDNA of each to work out if splicing differences are causing the other cell to use a different cleavage/polyadenylation site. And whether the splicing changes the position of the stop codon and the resulting protein size.
No, the transcript with the downstream polyadenylation will have a longer 3' UTR. mRNAs are usually not translated until their 3' end.
No. The transcript will be longer, but after translation the two derived proteins should have the same size. The 3'UTR size do not determine the protein size, the position of stop codon do this.
If both RNAs are the same sequence, except one has a longer 3'UTR, then the protein products will be the same size -translation will end at the stop codon, regardless of how much more downstream RNA there is. However, if one RNA has a different 3'UTR, it is possible that splicing may be different between the two RNAs and the longer RNA may have a different stop codon, which produces a longer protein. You need to look at the full length cDNA of each to work out if splicing differences are causing the other cell to use a different cleavage/polyadenylation site. And whether the splicing changes the position of the stop codon and the resulting protein size.
I fully concur with Amanda's response - quite often, differential 3' end processing is spatially and temporally tied to differential splicing.
That statement is false, like Niels said, alternative polyadenylation modifies the 3'UTR which doesn't have an effect on the c-terminus of the translated protein.
Given the language of the statement one cannot definitively say whether it is true or false as the text has "particular/same RNA" w/o specifying if it is pre-mRNA or mRNA (see my comment above), and then "necessarily" i.e. always so it is impossible to rule either way based on the info provided.
Hi Nghiem, I agree with the previous comments. The protein will be the same, but you can not exclude some changes in RNA stability or transport.
Do you mean an alternative termination site and polyadenylation dow stream and in phase with the first one. Did you look thouroughly at the sequence of the mRNA (DNA) you are working with??? This is the in silico part of the question.
After you can assume what happens at the level of protein expression (mRNA stability, protein stablity, etc.).
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