CHROMODOMAIN HELICASE DNA-BINDING PROTEIN 9; CHD9 ...

Shur and Benayahu (2005) cloned CHD9 from a human mesenchymal stromal cell (MSC) expression library. The deduced a 2,898-amino acid CHD9 protein has a calculated molecular mass of 320 kD. It contains an N-terminal bipartite nuclear localization signal, followed by 2 chromodomains, an SNF2 domain, a helicase-C domain, 3 conserved regions, a SANT domain that overlaps the third conserved region, a serine stretch, an A/T-hook DNA-binding domain, and 2 C-terminal BRK domains. Northern blot analysis of MSCs detected an 11-kb CHD9 transcript, and real-time PCR revealed low expression of CHD9 in MSCs. Western blot analysis showed that CHD9 protein was extensively phosphorylated posttranslationally on serine and tyrosine residues. Immunostaining of CHD9 revealed distribution of the protein throughout cytoplasm and nuclei of cultured MSCs. In vivo immunostaining of bone tissue showed CHD9 in marrow stromal osteoprogenitor cells, adjacent to but absent from mature osteoblasts.

Surapureddi et al. (2006) isolated Chd9, which they called Pric320, from a rat Ppara-binding complex, and they cloned full-length human CHD9 by database analysis and RACE using HeLa cell and LoVo adenocarcinoma cell total RNA. They identified 5 LxxLL signature motifs in human CHD9 that mediate interaction with nuclear receptors. Northern blot analysis detected low expression of an 11.5-kb transcript in various human tissues. Expression of CHD9 was higher in HeLa cells than other cancer cell lines. RT-PCR analysis showed Chd9 expression in all mouse tissues examined, with highest level in brain, followed by heart, kidney, and skeletal muscle.

Using Chd9-specific antisera, Salomon-Kent et al. (2015) observed expression of endogenous Chd9 in nucleolus of mouse MBA15 stromal cells, in addition to cytoplasmic and nuclear expression. They attributed the variable subcellular localization of Chd9 to differential phosphorylation. Immunofluorescence analysis showed colocalization of Chd9 with fibrillarin (FBL; 134795), upstream binding factor (UBTF; 600673), and RNA polymerase (pol) I (see 616404) in nucleoli, suggesting that nucleolar CHD9 has a role in ribosomal gene transcription.