Primary structural features of SR-like protein acinusS govern the phosphorylation mechanism by SRPK2.
SRPKs (serine/arginine protein kinases) are highly specific kinases that recognize and phosphorylate RS (Arg-Ser) dipeptide repeats. It has been shown previously that SRPK1 phosphorylates the RS domain of SRSF1 (serine/arginine splicing factor 1) at multiple sites using a directional and processive mechanism. Such ability to processively phosphorylate substrates is proposed to be an inherent characteristic of SRPKs. SRPK2 is highly related to SRPK1 in sequence and in vitro properties, yet it has been shown to have distinct substrate specificity and physiological function in vivo. To study the molecular basis for substrate specificity of SRPK2, we investigated the roles of the non-kinase regions and a conserved docking groove of SRPK2 in the recognition and phosphorylation of different substrates: SRSF1 and acinusS. Our results reveal that a conserved electronegative docking groove in SRPK2, but not its non-kinase regions, is responsible for substrate binding regardless of their identities. Although SRPK2 phosphorylates SRSF1 in a processive manner as predicted, an electronegative region on acinusS restricts SRPK2 phosphorylation to a single specific site despite the presence of multiple RS dipeptides. These results suggest that primary structural elements on the substrates serve as key regulatory roles in determining the phosphorylation mechanism of SRPK2.
*School of Life Sciences, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR.
Ning
N
Liang
*School of Life Sciences, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR.
Chuyue
C
Zeng
*School of Life Sciences, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR.
Kin Pong
KP
Tao
*School of Life Sciences, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR.
Weng Hong
WH
Sou
*School of Life Sciences, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR.
Ho Pan
HP
Hsia
*School of Life Sciences, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR.
Dan
D
Qu
*School of Life Sciences, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR.
Sze Nga
SN
Lau
*School of Life Sciences, the Chinese University of Hong Kong, Shatin, New Territories, Hong Kong SAR.
Jacky Chi Ki
JC
Ngo
D000595:Amino Acid Sequence; D045744:Cell Line, Tumor; D017124:Conserved Sequence; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics*; D010766:Phosphorylation / Q000502:physiology; D011485:Protein Binding / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics*; D013379:Substrate Specificity
C121310:ACIN1 protein, human; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; C110522:SRPK2 protein, human