Positive and negative regulation of poly(A) nuclease.
PAN, a yeast poly(A) nuclease, plays an important nuclear role in the posttranscriptional maturation of mRNA poly(A) tails. The activity of this enzyme is dependent on its Pan2p and Pan3p subunits, as well as the presence of poly(A)-binding protein (Pab1p). We have identified and characterized the associated network of factors controlling the maturation of mRNA poly(A) tails in yeast and defined its relevant protein-protein interactions. Pan3p, a positive regulator of PAN activity, interacts with Pab1p, thus providing substrate specificity for this nuclease. Pab1p also regulates poly(A) tail trimming by interacting with Pbp1p, a factor that appears to negatively regulate PAN. Pan3p and Pbp1p both interact with themselves and with the C terminus of Pab1p. However, the domains required for Pan3p and Pbp1p binding on Pab1p are distinct. Single amino acid changes that disrupt Pan3p interaction with Pab1p have been identified and define a binding pocket in helices 2 and 3 of Pab1p's carboxy terminus. The importance of these amino acids for Pab1p-Pan3p interaction, and poly(A) tail regulation, is underscored by experiments demonstrating that strains harboring substitutions in these residues accumulate mRNAs with long poly(A) tails in vivo.
Mangus
David A
DA
Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01655, USA.
Evans
Matthew C
MC
Agrin
Nathan S
NS
Smith
Mandy
M
Gongidi
Preetam
P
Jacobson
Allan
A
D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004271:DNA, Fungal / Q000235:genetics; D005095:Exoribonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010449:Peptide Mapping; D039102:Poly(A)-Binding Proteins / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021122:Protein Subunits; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
D004271:DNA, Fungal; D005095:Exoribonucleases; D039102:Poly(A)-Binding Proteins; D021122:Protein Subunits; D029701:Saccharomyces cerevisiae Proteins; C450100:pab1 protein, S cerevisiae; C101747:PAN3 protein, S cerevisiae