The sequence 5'-AAUAAA-3'forms parts of the recognition site for polyadenylation of late SV40 mRNAs

Area of Science:

• Molecular Biology
• Virology
• Genetics

Background:

• Polyadenylation is a crucial post-transcriptional modification of eukaryotic mRNAs.
• The AAUAAA sequence is a key cis-acting element regulating polyadenylation.
• SV40 late mRNAs provide a model system to study polyadenylation mechanisms.

Purpose of the Study:

• To investigate the effects of specific deletion mutations on the polyadenylation of SV40 late mRNAs.
• To determine the role of sequences flanking the AAUAAA motif in defining the polyadenylation site.
• To understand how deletions within or near the AAUAAA sequence influence polyadenylation.

Main Methods:

• Construction and analysis of deletion mutants in the SV40 genome.
• Identification and characterization of polyadenylation sites in mutant mRNAs using molecular techniques.
• Mapping of poly(A) sites relative to the AAUAAA sequence and deletion endpoints.

Main Results:

• Mutants lacking sequences between AAUAAA and the poly(A) site produced mRNAs polyadenylated at downstream sites, with site selection dependent on deletion size.
• Mutants with deletions between AAUAAA and the coding region showed altered spatial relationships, leading to heterogeneous polyadenylation.
• A deletion encompassing the AAUAAA sequence abolished polyadenylation.

Conclusions:

• The region between AAUAAA and the poly(A) site influences downstream polyadenylation site selection.
• The spatial arrangement of AAUAAA relative to downstream sequences is critical for precise polyadenylation.
• The AAUAAA motif itself is essential for the initiation of polyadenylation.