Identification of two novel human dynein light chain genes, DNLC2A and DNLC2B, and their expression changes in hepatocellular carcinoma tissues from 68 Chinese patients.

Two full-length cDNAs, DNLC2A and DNLC2B, were cloned and characterized. Their open reading frames respectively encode 96 amino acids which are most closely homologous to roadblock/LC7, one member of an ancient dynein light chain protein family, conserved in nematode, fruit fly, mouse and rat. The DNLC2A was expressed in 12 of 16 human tissues examined, with especially strong expression in heart, liver and brain, whereas there was weak expression in lung, prostate, testis, small intestine and colon. The expression of DNLC2B was generally high compared with that of DNLC2A except in liver. Northern blotting and/or semi-quantitative RT-PCR analysis examined the expression changes of DNLC2A and DNLC2B in 68 hepatocellular carcinoma tissue samples. It was revealed that DNLC2A was up-regulated (45 out of the 68 cases) while DNLC2B was down-regulated (44 out of 68 cases), compared with their adjacent tumor-free liver tissues. Interestingly, among the total 68 liver cancer samples tested, DNLC2A was up-regulated while DNLC2B was down-regulated in 28 cases; DNLC2A was up-regulated while no obvious change was observed for DNLC2B in 10 cases; no obvious change was observed for DNLC2A while DNLC2B was down-regulated in 14 cases. Although the underlying mechanism is not clear to date, the apparent up-regulation of DNLC2A and down-regulation of DNLC2B suggest that these genes might be involved in tumor progression. On the other hand, the different expression changes of the two homologous genes indicate that hepatocellular carcinomas are caused by different pathological mechanisms. In addition, DNLC2A was assigned to human chromosome 20q12-q13.11 near the marker D20S106 by radiation hybrid mapping.