MOLECULAR-CLONING AND SUBCELLULAR-LOCALIZATION OF THE SNRNP-ASSOCIATED PROTEIN 69KD, A STRUCTURAL HOMOLOG OF THE PROTO-ONCOPROTEINS TLS ANDEWS WITH RNA AND DNA-BINDING PROPERTIES

We recently isolated and characterised a 69 kDa protein (69KD) found a ssociated with spliceosomal small nuclear ribonucleoproteins (snRNPs). Here, we report the molecular cloning of a cDNA encoding this protein , its nucleic acid binding properties and its subcellular localisation . Sequence analysis of the 69KD cDNA revealed: (1) that 69KD shares st ructural similarity with the human RNA binding proteins TLS and EWS (9 5% and 65% identity, respectively), the products of two genes frequent ly targeted by tumour-specific chromosomal translocations; (2) that 69 KD contains a consensus RNA binding domain (CS-RBD) and three Arg/Gly- rich RNA binding motifs, structural features typical of many RNA bindi ng proteins, in particular of hnRNP proteins; and (3) that 69KD contai ns a single putative Cys(2)/Cys(2) zinc finger domain, a characteristi c of many DNA-binding proteins. Consistent with its possession of thes e motifs, 69KD display a general nucleic acid binding activity, with a strong preference for guanyl and uridyl-rich RNA sequences, as well a s for single-stranded and double-stranded DNA. The functional signific ance of this affinity for nucleic acids remains unclear. However, base d on the established association of 69KD with the Sm core domain of sn RNPs in vivo, these motifs might help mediate 69KD binding to snRNPs o r be involved in some, as yet, unknown aspect of RNA metabolism. Consi stent with both possibilities, 69KD is detected within typical snRNP c ontaining subnuclear structures referred to as speckles, and is also m ore widely distributed throughout the nucleoplasm, as observed for man y hnRNP proteins. (C) 1996 Academic Press Limited.