Isolation of a maize bZIP protein subfamily: candidates for the ocs-element transcription factor.
Ocs-elements, a family of 20 bp DNA sequences, are components of a number of promoters active in plants. In the maize BMS cell line the dominant ocs-element binding activity is the ocs-element transcription factor complex called OTF. The isolation of cDNA clones from a BMS cDNA expression library for two bZIP (basic region-leucine zipper) proteins that bind the ocs-element sequence and are good candidates for forming at least part of OTF is described. The two ocs-element binding proteins, called OBF3.1 and OBF3.2, are closely related, with the OBF3.1 protein sharing 95.8% amino acid homology with part of the OBF3.2 protein although there were significant differences in the 3' untranslated regions. Genomic Southern blot analysis revealed a small gene family with a minimum of two OBF3 loci mapping to chromosomes 3L105 and 8L075. The OBF3.1 protein shared considerable homology with the wheat HBP1b protein (80% amino acid identity) and to a lesser extent with the tobacco TGA1aa protein. OBF3.1 like HBP1b was able to bind well to the Hex sequence but poorly to G-box/ABRE sequences. Interestingly, OBF3.1 bound eightfold more efficiently to an ocs-element sequence than TGA1a, raising the possibility that OBF3.1 and TGA1a may be distinct members of an OBF3/TGA subfamily.
Department of Biology, University of California, Los Angeles 90024.
R C
RC
Foley
C
C
Grossman
J G
JG
Ellis
D J
DJ
Llewellyn
E S
ES
Dennis
W J
WJ
Peacock
K B
KB
Singh
D000595:Amino Acid Sequence; D001483:Base Sequence; D050976:Basic-Leucine Zipper Transcription Factors; D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D017343:Genes, Plant; D016350:Leucine Zippers / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D010940:Plant Proteins / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D010947:Plants, Toxic; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana; D014157:Transcription Factors / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D014908:Triticum; D003313:Zea mays / Q000737:chemistry* / Q000235:genetics
D050976:Basic-Leucine Zipper Transcription Factors; C083302:OBF3.1 protein, Zea mays; C083303:OBF3.2 protein, Zea mays; D010940:Plant Proteins; D014157:Transcription Factors; D004247:DNA