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.
Graduate School of Biological Sciences, Nara Institute of Science and Technology Takayama 8916-5, Ikoma, Nara, 630-0101, Japan. yoshida@salk.edu
Tomonori
T
Yoshida
Tsuyoshi
T
Ohkumo
Shoko
S
Ishibashi
Kunio
K
Yasuda
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