ZBP-99 defines a conserved family of transcription factors and regulates ornithine decarboxylase gene expression.
Among transcription factors that regulate ornithine decarboxylase (ODC) gene expression are those that interact with GC-rich promoters, including Sp1 and ZBP-89. Sp1 functions as a transactivator and ZBP-89 as a transrepressor of both the ODC and gastrin promoters. This study reports the cloning and characterization of a second member of the ZBP family that also binds GC boxes. ZBP-99 contains four Krüppel-type zinc fingers that collectively share 91% amino acid sequence similarity and 79% sequence identity with those found in ZBP-89. In addition, there are highly conserved amino acid sequences in the carboxy-terminal segments of the two genes. In spite of their structural similarities, the two proteins are encoded at distinct loci, ZBP-89 on chromosome 3q21 and ZBP-99 on 1q32.1. The predicted open reading frame of ZBP-99 cDNA encodes a 99-kDa protein. Electrophoretic mobility shift assays showed that ZBP-99 protein specifically binds to the GC-rich promoter elements of gastrin and ODC genes. Northern blot analysis showed that a major ZBP-99 transcript of 5.6 kb is expressed ubiquitously at low levels, with elevated expression levels in placenta and in adult kidney, liver, and lymphocytes. Cotransfection of AGS gastric adenocarcinoma and HT-29 colon adenocarcinoma cells with a ZBP-99 expression construct and with an ODC reporter construct show that ZBP-99 repressed basal expression in the two cell lines by 80 and 60%, respectively. Collectively, the data suggest that ZBP-99 binds GC-rich promoters and may complement the activities mediated by ZBP-89.
Law
D J
DJ
Department of Internal Medicine, Department of Physiology, University of Michigan, Michigan, Ann Arbor 48109-0650, USA.
Du
M
M
Law
G L
GL
Merchant
J L
JL
D000595:Amino Acid Sequence; D001483:Base Sequence; D002878:Chromosomes, Human, Pair 1 / Q000235:genetics; D003001:Cloning, Molecular; D017124:Conserved Sequence / Q000235:genetics*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005755:Gastrins / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008969:Molecular Sequence Data; D009955:Ornithine Decarboxylase / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015534:Trans-Activators; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D016335:Zinc Fingers
D004268:DNA-Binding Proteins; D005755:Gastrins; D012333:RNA, Messenger; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C110951:ZNF148 protein, human; C120370:ZNF281 protein, human; D004247:DNA; D009955:Ornithine Decarboxylase