The RNA binding domains of the nuclear poly(A)-binding protein.
The nuclear poly(A)-binding protein (PABPN1) is involved in the synthesis of the mRNA poly(A) tails in most eukaryotes. We report that the protein contains two RNA binding domains, a ribonucleoprotein-type RNA binding domain (RNP domain) located approximately in the middle of the protein sequence and an arginine-rich C-terminal domain. The C-terminal domain also promotes self-association of PABPN1 and moderately cooperative binding to RNA. Whereas the isolated RNP domain binds specifically to poly(A), the isolated C-terminal domain binds non-specifically to RNA and other polyanions. Despite this nonspecific RNA binding by the C-terminal domain, selection experiments show that adenosine residues throughout the entire minimal binding site of approximately 11 nucleotides are recognized specifically. UV-induced cross-links with oligo(A) carrying photoactivatable nucleotides at different positions all map to the RNP domain, suggesting that most or all of the base-specific contacts are made by the RNP domain, whereas the C-terminal domain may contribute nonspecific contacts, conceivably to the same nucleotides. Asymmetric dimethylation of 13 arginine residues in the C-terminal domain has no detectable influence on the interaction of the protein with RNA. The N-terminal domain of PABPN1 is not required for RNA binding but is essential for the stimulation of poly(A) polymerase.
Kühn
Uwe
U
Institut für Biochemie, Martin-Luther-Universität Halle, 06099 Halle, Germany.
Nemeth
Anne
A
Meyer
Sylke
S
Wahle
Elmar
E
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism; D039102:Poly(A)-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism
D009687:Nuclear Proteins; D039102:Poly(A)-Binding Proteins; D012313:RNA