DIRECT INTERACTION OF THE KRAB CYS(2)-HIS(2) ZINC-FINGER PROTEIN ZNF74 WITH A HYPERPHOSPHORYLATED FORM OF THE RNA-POLYMERASE-II LARGEST SUBUNIT/

We previously identified ZNF74 as a developmentally expressed gene com monly deleted in DiGeorge syndrome. ZNF74 encodes an RNA-binding prote in tightly associated with the nuclear matrix and belongs to a large s ubfamily of Cys(2)-His(2) zinc finger proteins containing a KRAB (Krup pel-associated box) repressor motif, We now report on the multifunctio nality of the zinc finger domain of ZNF74, This nucleic acid binding d omain is shown here to function as a nuclear matrix targeting sequence and to be involved in protein-protein interaction, Ey far-Western ana lysis and coimmunoprecipitation studies, we demonstrate that ZNF74 int eracts, via its zinc finger domain, with the hyperphosphorylated large st subunit of RNA polymerase II (pol IIo) but not with the hypophospho rylated form. The importance of the phosphorylation in this interactio n is supported by the observation that phosphatase treatment inhibits ZNF74 binding. Double immunofluorescence experiments indicate that ZNF 74 colocalizes with the pol IIo and the SC35 splicing factor in irregu larly shaped subnuclear domains, Thus, ZNF74 sublocalization in nuclea r domains enriched in pre-mRNA maturating factors, its RNA binding act ivity, and its direct phosphodependent interaction with the pol IIo, a form of the RNA polymerase functionally associated with pre-mRNA proc essing, suggest a role for this member of the KRAB multifinger protein family in RNA processing.