Identification and functional study of a novel gene (C15ORF65) in normal and malignant hematopoiesis

Abstract

In a previous collaborative study, C150RF65 (also known as FLJ27352, BX648577, and hypothetical LOC 145788) was identified as a truncated fusion partner of the major histocompatibility complex (MHC) class II transactivator CIITA in a Hodgkin's Lymphoma cell line (Steidl C et al., Nature 2011). The objective of the current study was to investigate the uncharacterized putative gene locus C150RF65, to assess whether this locus encodes and expresses full length mRNA and protein, and to assess its biological function in normal and malignant hematopoietic cells. We found that the C150RF65 locus is highly conserved across species and detected endogenous mRNA and protein expression in human and murine primary hematopoietic cells of different maturity and lineages, as well as in human leukemia cell lines. Using lentiviral gain-of-function and loss-of-function assays, we found that C150RF65 positively regulated cell proliferation, colony formation ability and cycling of aberrant hematopoietic cells. Experimental downregulation of C150RF65 significantly inhibited in vivo growth of acute myeloid leukemia cells, while it had no effect on normal CD34 + cells. C150RF65 overexpression led to increased proliferative capacity concomitant with increased cell cycling and activation of the KRAS signâling pathway. Additionally Ingenuity Pathway Analysis (IPATM) after microarray analysis of NB4 cells overexpressing C150RF65 revealed enrichment in cell cycle progression and proliferation processes, in line with our observations at the functional level. In summary, in this study, we demonstrate for the first time mRNA and protein expression of the gene encoded by the putative C150RF65 gene locus. Additionally we show that C150RF65 is essential for regulating cell cycling and growth in aberrant hematopoietic cells, specifically in myeloid malignancies. Further studies are warranted to investigate the upstream regulators and downstream targets of this novel protein coding gene. We propose the new gene name Regulator of cell proliferation (ROCP), referring to its newly identified function.