Question

Explain how the use of alternative promoters and alternative polyadenylation signals produces mRNAs with different - and -ends.

Accepted Answer

Understand that alternative promoters are different DNA sequences located upstream of a gene that can initiate transcription at different start sites, leading to mRNAs with variable 5'-ends. Recognize that the choice of an alternative promoter affects which exon is included at the 5'-end of the mRNA, thus producing transcripts with different 5' untranslated regions (5' UTRs) or even different coding sequences. Know that alternative polyadenylation signals are different sequences within the gene that signal where the mRNA should be cleaved and a poly(A) tail added, resulting in mRNAs with different 3'-ends. Realize that the use of alternative polyadenylation sites can change the length of the 3' untranslated region (3' UTR) or even affect the coding sequence if polyadenylation occurs within an exon. Combine these concepts to explain that by using different promoters and polyadenylation signals, a single gene can produce multiple mRNA isoforms that differ at their 5' and 3' ends, which can influence mRNA stability, localization, and translation efficiency.

Explain how the use of alternative promoters and alternative polyadenylation signals produces mRNAs with different - and -ends.

Concetti chiave

Alternative Promoters

Alternative Polyadenylation Signals

mRNA End Processing and Regulation