Identification and characterization of ASXL2 gene in silico.

Drosophila Asx is a Polycomb group gene. Because Drosophila Asx mutations exhibit anterior and posterior transformations, Drosophila Asx is one of the ETP (Enhancers of trithorax and Polycomb) genes with dual functions in transcriptional activation and silencing. ASXL1 is one of human homologs of Drosophila Asx. Here, we searched for ASXL1-related gene within the human genome by using bioinformatics, and identified the ASXL2 gene. Nucleotide sequence of human ASXL2 cDNA was determined by assembling the nucleotide sequences of human EST AI797346, and partial cDNAs MGC44431 (BC042999) and KIAA1685 (AB051472). Nucleotide sequence of mouse Asxl2 was derived from uncharacterized mouse cDNA 9930017F14 (AK036839). Human ASXL2 (1435 aa) showed 79.4% total-amino-acid identity with mouse Asxl2 (1370 aa), and 29.8% total-amino-acid identity with human ASXL1. ASXN domain (codon 1-86 of ASXL2), ASXM domain (codon 269-380 of ASXL2), and PHD domain (codon 1400-1431 of ASXL2) were conserved between human ASXL2 and ASXL1. Human ASXL2 gene, consisting of at least 13 exons, was mapped to human chromosome 2p23.3, one of recombination hot spots or fragile sites associated with carcinogenesis. The DNMT3A-ASXL2-KIF3C locus on human chromosome 2p23.3 and the DNMT3B-ASXL1-KIF3B locus on human chromosome 20q11.21 were paralogous regions within the human genome. Polycomb group and trithorax group proteins are implicated in embryogenesis and carcinogenesis due to transcriptional regulation of target genes through histone modification and chromatin remodeling. Based on functional conservation and human chromosomal localization, ASXL2 and ASXL1 genes were predicted cancer-associated genes.