1. ¹Key Laboratory of Human Functional Genomics of Jiangsu Province, Nanjing Medical University, Nanjing, PR China
2. ²Department of Cell Biology and Medical Genetics, Nanjing Medical University, Nanjing, PR China
3. ³School of Pharmacy, Nanjing Medical University, Nanjing, PR China
4. ⁴Department of Molecular Medicine, City of Hope National Medical Center, Duarte, CA, USA

Correspondence: Dr Y Sun and Dr X Han, Key Laboratory of Human Functional Genomics of Jiangsu Province, College of Basic Medicine, Nanjing Medical University, Hanzhong Rd. #140, Nanjing 210029, PR China. E-mail: yujiesun@njmu.edu.cn and hanxiao@njmu.edu.cn

Received 26 February 2006; Revised 23 August 2006; Accepted 4 September 2006; Published online 23 October 2006.

Abstract

BCL2 expression is finely tuned by a variety of environmental and endogenous stimuli and regulated at both transcriptional and post-transcriptional levels. Our previous investigations demonstrated that the BCL2 major breakpoint region (mbr) in the 3'-UTR upregulates reporter gene expression, which implies that this region possessed intrinsic regulatory function. However, the effect of the mbr on BCL2 expression, and the underlying regulatory mechanisms, remain to be elucidated. To assess the direct effect of the mbr on the transcriptional activity of the BCL2 gene, we employed targeted homologous recombination to establish a mbr⁺/mbr^- heterozygous Nalm-6 cell line and then compared the transcriptional activity and apoptotic effect on transcription between the wild type and targeted alleles. We found that deletion of the mbr significantly decreased the transcriptional activity of the corresponding allele in the mbr⁺/mbr^- cell. The BCL2 allele deleted of the mbr had a slower response to apoptotic stimuli than did the wild type allele. The regulatory function of the mbr was mediated through SATB1. Overexpression of SATB1 increased BCL2 expression, while knockdown of SATB1 with RNAi decreased BCL2 expression. Our results clearly indicated that the mbr could positively regulate BCL2 gene expression and this regulatory function was closely related to SATB1.