Characterization of the 5'-flanking region of the human DNA helicase B (HELB) gene and its response to trans-Resveratrol.

Human DNA helicase B (HELB/HDHB) regulates DNA replication through association with human DNA polymerase α-primase. In the present study, an 866-base pair (bp) of the 5'-flanking region of the human HELB gene-containing Luciferase (Luc) reporter plasmid, pHDHB-Luc was transfected into various cell lines and Luc activity was analyzed. Deletion analyses revealed that a 121-bp containing the major transcription start site (TSS) was essential for the basal promoter activity in all tested cells. TF-SEARCH analysis indicated that GC-box/Sp1 and duplicated GGAA-motifs containing putative STAT-x and c-ETS binding sites are located close to the TSS. Furthermore, chromatin immunoprecipitation (ChIP) analysis showed that PU.1 and Sp1 bind to the 121-bp region. Reverse transcriptase-polymerase chain reaction (RT-PCR) and western blot analyses showed the HELB gene and protein expression was up-regulated by trans-Resveratrol (Rsv) treatment in HeLa S3 cells. Moreover, transfection experiment indicated that mutations on the GC-boxes and the duplicated GGAA-motif greatly reduced promoter activity and the response to Rsv in HeLa S3 cells. These results suggest that Rsv, which is a natural compound that has been found to elongate the lifespan of various organisms, regulates HELB promoter activity through co-operation of the GC-boxes and the duplicated GGAA-motif in the 121-bp.