PAP-1, the mutated gene underlying the RP9 form of dominant retinitis pigmentosa, is a splicing factor.
PAP-1 is an in vitro phosphorylation target of the Pim-1 oncogene. Although PAP-1 binds to Pim-1, it is not a substrate for phosphorylation by Pim-1 in vivo. PAP-1 has recently been implicated as the defective gene in RP9, one type of autosomal dominant retinitis pigmentosa (adRP). However, RP9 is a rare disease and only two missense mutations have been described, so the report of a link between PAP-1 and RP9 was tentative. The precise cellular role of PAP-1 was also unknown at that time. We now report that PAP-1 localizes in nuclear speckles containing the splicing factor SC35 and interacts directly with another splicing factor, U2AF35. Furthermore, we used in vitro and in vivo splicing assays to show that PAP-1 has an activity, which alters the pattern of pre-mRNA splicing and that this activity is dependent on the phosphorylation state of PAP-1. We used the same splicing assay to examine the activities of two mutant forms of PAP-1 found in RP9 patients. The results showed that while one of the mutations, H137L, had no effect on splicing activity compared with that of wild-type PAP-1, the other, D170G, resulted in both a defect in splicing activity and a decreased proportion of phosphorylated PAP-1. The D170G mutation may therefore cause RP by altering splicing of retinal genes through a decrease in PAP-1 phosphorylation. These results demonstrate that PAP-1 has a role in pre-mRNA splicing and, given that three other splicing factors have been implicated in adRP, this finding provides compelling further evidence that PAP-1 is indeed the RP9 gene.
Maita
Hiroshi
H
Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo 060-0812, Japan.
Kitaura
Hirotake
H
Keen
T Jeffrey
TJ
Inglehearn
Chris F
CF
Ariga
Hiroyoshi
H
Iguchi-Ariga
Sanae M M
SM
D017304:Annexin A5 / Q000235:genetics* / Q000378:metabolism; D005914:Globins / Q000096:biosynthesis / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D007075:Immunoglobulin M / Q000096:biosynthesis / Q000235:genetics; D009154:Mutation; D015530:Nuclear Matrix / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D000073718:Pancreatitis-Associated Proteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051573:Proto-Oncogene Proteins c-pim-1; D012326:RNA Splicing / Q000502:physiology*; D000072260:RNA Splicing Factors; D012174:Retinitis Pigmentosa / Q000235:genetics* / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism; D000072668:Splicing Factor U2AF
D017304:Annexin A5; D007075:Immunoglobulin M; D009687:Nuclear Proteins; D000073718:Pancreatitis-Associated Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; C000612141:REG3A protein, human; D000072260:RNA Splicing Factors; C465969:RP9 protein, human; D012261:Ribonucleoproteins; D000072668:Splicing Factor U2AF; C076753:U2AF1 protein, human; D005914:Globins; C496634:PIM1 protein, human; D017346:Protein Serine-Threonine Kinases; D051573:Proto-Oncogene Proteins c-pim-1