The 5'-AT-rich half-site of Maf recognition element: a functional target for bZIP transcription factor Maf.
The Maf family of proteins are a subgroup of basic region-leucine zipper (bZIP) transcription factors, which recognize a long palindromic DNA sequence [TGCTGAC(G)TCAGCA] known as the Maf recognition element (MARE). Interestingly, the functional target enhancer sequences present in the alphaA-crystallin gene contain a well-conserved half-site of MARE rather than the entire palindromic sequence. To resolve how Maf proteins bind to target sequences containing only MARE half-sites, we examined their binding activities using electrophoretic gel mobility shift assays as well as in vitro and in vivo reporter assays. Our results indicate that the 5'-flanking region of the MARE half-site is required for Maf proteins to bind both in vitro and in vivo. The critical 5'-flanking sequences for c-Maf were determined by a selection and amplification binding assay and show a preference for AT-rich nucleotides. Furthermore, sequence analysis of the regulatory regions of several target genes also suggests that AT-rich sequences are important. We conclude that Maf can bind to at least two types of target sequences, the classical MARE (palindrome type) and a 5'-AT-rich MARE half-site (half-site type). Our results provide important new insights into the DNA binding and site selection by bZIP transcription factors.
Yoshida
Tomonori
T
Graduate School of Biological Sciences, Nara Institute of Science and Technology Takayama 8916-5, Ikoma, Nara, 630-0101, Japan. yoshida@salk.edu
Ohkumo
Tsuyoshi
T
Ishibashi
Shoko
S
Yasuda
Kunio
K
D024506:5' Flanking Region; D020856:AT Rich Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D050977:Maf Transcription Factors; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D051257:Proto-Oncogene Proteins c-maf; D020218:Response Elements; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014982:Xenopus laevis
D004268:DNA-Binding Proteins; C111440:L-MAF protein, Gallus gallus; D050977:Maf Transcription Factors; D011518:Proto-Oncogene Proteins; D051257:Proto-Oncogene Proteins c-maf; D014157:Transcription Factors