A Myc-associated Zinc Finger Protein-related Factor Binding Site Is Required for the Deregulation of c-mycExpression by the Immunoglobulin Heavy Chain Gene Enhancers in Burkitt's Lymphoma

Hsien-Ming Hu,Magdalena Arcinas,Linda M Boxer

doi:10.1074/jbc.m111426200

Abstract

The deregulation of expression of the c-myc gene in Burkitt's lymphoma results from the translocation that links one c-myc allele to one of the immunoglobulin genes. This physical linkage promotes interactions between c-myc and immunoglobulin gene regulatory elements that affect c-myc transcription initiation and elongation. We have located a region in the c-myc promoter that is required for the complete activation by the immunoglobulin heavy chain gene enhancer. This regulatory element contains a core sequence, GGGAGG, similar to the GA box recognized by the transcription factor Myc-associated zinc finger protein (MAZ). UV cross-link analysis indicated that the mass of this protein did not correspond to that of MAZ, suggesting that a protein related to but distinct from MAZ bound to this site. Mutation of this regulatory element resulted in a loss of promoter activity induced by the immunoglobulin heavy chain gene enhancer. This site was also required for the c-myc promoter shift from P2 to P1. In vivo footprinting revealed that this site was occupied on the translocated c-myc allele but not on the untranslocated allele. Taken together, these findings suggest that this regulatory element is required for the full activation of c-myc promoter activity by the immunoglobulin heavy chain gene enhancer.

Highlights

A Myc-associated Zinc Finger Protein-related Factor Binding Site Is Required for the Deregulation of c-myc Expression by the Immunoglobulin Heavy Chain Gene Enhancers in Burkitt’s Lymphoma*
Identification of a Regulatory Element in the c-myc Promoter That Is Required for Activated Expression of c-myc—To search for the promoter regulatory elements required for the activation of c-myc transcription by the immunoglobulin heavy chain gene (IgH) enhancer, reporter constructs containing serial 5Ј deletions of the c-myc promoter region were generated (Fig. 1, A and B)
The regulation of expression of the translocated c-myc allele in these variants may involve different sets of transcription factors that bind to the c-myc promoter region and interact with IgH enhancer elements

Summary

The abbreviations used are

IgH, immunoglobulin heavy chain gene; MHS, murine hypersensitive site(s); MAZ, Myc-associated zinc finger protein; EMSA, electrophoretic mobility shift assay; NF-␬B, nuclear factor-␬B; MAZ-R, MAZ-related. Transcription factors such as Sp1 [10, 11], Myc-associated zinc finger protein (MAZ) [12, 13], and E2F [14] have been reported to bind to three cis-elements located between the P1 and P2 start sites These sites are required for the basal activity of the P2 promoter in proliferating cells; their roles in the deregulation of the c-myc gene in Burkitt’s lymphoma cells have not been fully studied. Located Ϫ523 bp upstream of the P1 transcription start site is required for the transcriptional activation of the translocated c-myc gene and that it is involved in inducing the promoter shift mediated by the IgH enhancer This element contains a GA box binding core, which is similar to that of a zinc finger transcription factor, MAZ. We evaluated the effect of the Sp1 site in the P1 core promoter on the activation of c-myc transcription by the IgH enhancer

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION