HSPC070, a novel ring finger protein gene, is preferentially expressed in myelocytic lineage and involved in g-protein mediated signal transduction

In a recent work, we identified 9866 ESTs from cord blood originated CD34+ hematopoietic stem/ progenitor cells. From these ESTs, 300 cDNAs containing entire open reading frames for previously undefined genes were cloned. HspcOVO, one of these novel gene cDNAs, was found to bear 3050bp encoding a protein of 416 amino acids. Northern blot showed that it is widely expressed in different human tissues but preferentially in hematopoietic cell line K562, NB4 and BJAB. Structure and functional prediction with bioinformatics tools revealed that it contains a typical C3HC4 RING finger motif. To further address its biological functions in the context of protein-protein interaction, yeast-two hybrid Gal4 system was applied, and a G protein beta-2 subunit was picked out and found to interact on Hspc070. The specificity of this interaction was confirmed with the GST-pull-down test. Further study using yeast-two hybrid system revealed that hspc070 might also interact with several ubiquitin-like proteins. These findings suggested that HSPC070 might be involved in the regulation of G protein mediated signal transduction pathway through degradation of some effective molecules. Now we are performing in vivo immunoprecipitation to further confirm the existence of this G protein beta-2/Hspc070/ubiquitin-like protein complex. The physiological role of this putative protein-protein interaction will also be examined.