Background In our previous study, we found that DAZAP2 was the most significantly down regulated gene when differential screening of complementary DNA （cDNA） chips were used to analyze mRNA isolated from bone marrow mononuclear cells from newly diagnosed multiple myeloma （MM） patients without anticancer treatment. In this study, we observed DAZAP2 mRNA and protein expression in the mononuclear cells from MM bone marrow and investigated its role in the pathogenesis of MM. Methods The full-length cDNA of DAZAP2 was cloned and sequenced from mononuclear cells from human bone marrow. The nucleotide and amino acid sequences of DAZAP2 were analyzed using the ClustalW program. A dendrogram was constructed by multiple sequence alignment using ClustalW and amino acid sequence identity/similarity was derived based on comparisons attained using the MegAlign software. The recombinant pEGFP expression vector was constructed and the confocal microscopy was used for the localization of the DAZAP2 protein in transfected COS7 cells. The expression of DAZAP2 mRNA was detected by semi-quantitative reverse transcription polymerase chain reaction （RT-PCR） and the expression level of DAZAP2 protein was detected by Western blotting analysis in MM samples. Results DAZAP2 proteins of vertebrates is highly conserved in evolution. It contains a proline-rich region, several potential SH2 and SH3 domain-binding motifs and a possible protein kinase C （PKC） phosphorylation site. We showed by confocal microscopy that the DAZAP2 protein predominantly resides in the cytoplasm with a discrete pattern of punctuated distribution. The expression of DAZAP2 was not detected in 24 of 36 MM samples by semi-quantitative RT-PCR. In contrast, DAZAP2 expression was detected in all 30 normal controls. The expression level of DAZAP2 protein was assayed by Western blotting analysis, showing a robust down-regulation in MM patients （P〈0.001） that matched with the results of the RT-PCR. Conclusions DAZAP2 is downregulated in MM samples and it
SHI Yi-wuSHEN RongREN WeiTANG Li-junTAN Da-renHU Wei-xin
In our previous studies, DAZAP2 gene expression was down-regulated inuntreated patients of multiple myeloma (MM). For better studying the structure and function ofDAZAP2, a full-length cDNA was isolated from mononuclear cells of a normal human bone marrow,sequenced and deposited to Genbank (AY430097). This sequence has an identical ORF (open readingframe) as the NM.014764 from human testis and the D31767 from human cell line KG-1. Phylogeneticanalysis and structure prediction reveal that DAZAP2 homologues are highly conserved throughoutevolution and share a polyproline region and several potential SH2/SH3 binding sites. DAZAP2 occursas a single-copy gene with a four-exon organization. We further noticed that the functional DAZAP2gene is located on Chromosome 12 and its pseudogene gene is on Chromosome 2 with electronic locationof human chromosome in Genbank, though no genetic abnormalities of MM have been reported onChromosome 12. The ORF of human DAZAP2 encodes a 17-kDa protein, which is highly similar to mousePrtb. The DAZAP2 protein is mainly localized in cytoplasm with a discrete pattern of punctuateddistribution. DAZAP2 may associate with carcinogenesis of MM and participate in yet-to-be identifiedsignaling pathways to regulate proliferation and differentiation of plasma cells.
