Identification of thecis-regulatory DNA element and the trans-acting factor maintaining constitutive expression of the avianmax gene
Abstract
Max is a nuclear phosphoprotein with a basic/helix-loop-helix/leucine zipper (b/HLH/LZ) region that forms heterodimers with the b/HLH/LZ oncoprotein Myc to regulate genes through Myc E-box sequiences within DNA. Max also forms homodimers and heterodimers with other members of the b/HLH/LZ family of proteins and directs these protein complexes to the same DNA binding sites as Myc-Max complexes. Several studies have demonstrated that there is a constant intracellular pool of Max protein which is required to support, or to prevent, gene expression regulated by b/HLH/LZ family members. The global role of Max in directing the activities of several transcriptional regulators, including the oncoprotein Myc, necessitates that Max expression be maintained at constant levels in all cells. This study has led to the identification of a minimal regulatory region, or MRR, within the 5$\sp\prime$ flanking region of the chicken max gene. The MRR comprises 115 bp 5$\sp\prime$ to the max translation initiation site and possesses an overall structure typical of TATA-less promoters. Within the MRR are two consensus binding sites for Sp1, an ubiquitously expressed transcription factor that plays a role in the expression of many constitutively expressed genes. Interestingly, direct binding by Sp1 to these sites is not required for MRR-mediated transcription. Instead, the integrity of a 20 bp DNA element in the MRR is required for transcriptional activity, as is the interaction of this DNA element with a cellular protein of approximately 90 kDa. The data in this study suggest that it is the persistence of this 90 kDa protein in vertebrate cells which drives max gene expression, insulates the max promoter from the dramatic changes in transcription that accompany cell growth and development and ensures that adequate levels of Max will be available to facilitate the function of the Myc family of b/HLH/LZ transcriptional regulators.
Degree
Ph.D.
Advisors
Taparowsky, Purdue University.
Subject Area
Molecular biology
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.