XXXX phosphorylation of a M(r) 38,000 A/B-type hnRNP protein selectively modulates its RNA binding.

@entity2228 @entity71357 @entity535 @entity22892 @entity669 @entity238
The M(r) 38,000 RNA-binding protein ( @entity71357 ) is the major component of translationally repressed messenger ribonucleoproteins in cryptobiotic gastrulae of the brine shrimp Artemia. Partial elucidation of the @entity535 sequence of @entity71357 reveals that it is homologous to A/B-type hnRNP proteins. This was confirmed by immunodetection with antibodies specific for A/B-type hnRNP proteins from @entity238 . @entity71357 can be phosphorylated in vitro by a src-related protein @entity669 kinase on multiple @entity669 residues located predominantly in the @entity2228 -rich domain. @entity669 phosphorylated @entity71357 can be efficiently dephosphorylated by a specific protein @entity669 phosphatase (1B-like) and by protein phosphatase 2A activated by the phosphotyrosyl phosphatase activator. @entity669 phosphorylation of @entity71357 slightly influences its subsequent phosphorylation by @entity22892 . The latter phosphorylation site is located in the @entity2228 -rich domain of @entity71357 . Two-dimensional gel electrophoresis resolves @entity71357 into multiple isoforms which shift to more acidic pI values after phosphorylation by protein @entity669 kinase or @entity22892 . From nitrocellulose filter binding and UV cross-linking analysis, evidence was obtained that @entity669 phosphorylation of @entity71357 impairs its binding to poly(A) but not to poly(U). This demonstrates the involvement of @entity669 residues in polynucleotide-specific RNA binding that can be regulated by phosphorylation/dephosphorylation.
