GRIF 1 and OIP 106 are modified by O GlcNAc and therefore are substrates for OGT . ^^^ Chem . 277 , 30079 30090 ) , and its novel homolog , OIP 106 ( KIAA 1042 ) , as novel OGT interacting proteins . ^^^ Both GRIF 1 and OIP 106 contain coiled coil domains and interact with the tetratricopeptide repeats of OGT . ^^^ However , unlike another high affinity protein substrate , such as nucleoporin p 62 , OIP 106 and GRIF 1 co immunoprecipitate with OGT , exhibiting stable in vitro and in vivo associations . ^^^ Co immunoprecipitation experiments confirm the presence of an in vivo RNA polymerase 2 OIP 106 OGT complex , suggesting that OIP 106 may target OGT to transcriptional complexes for glycosylation of transcriptional proteins , such as RNA polymerase 2 , and transcription factors . ^^^ |