Characterization of the 5'-flanking region of the rat AJ18 gene.
Krüppel-associated box (KRAB) domains are present in one-third of all C(2)H(2) zinc finger containing proteins, making the KRAB/C(2)H(2) proteins one of the largest known families of putative transcription repressors. AJ18 has been identified as a novel KRAB/C(2)H(2) gene that is involved in the differentiation of osteogenic cells. To study the regulation of expression of the AJ18 gene, the 5'-flanking region of the AJ18 gene was obtained by screening a rat genomic library. This region was sequenced, and the transcription start site mapped by primer extension. The AJ18 gene consists of at least four exons, the first exon coding for an unusually long 2.3 kb 5'-UTR region. A putative internal ribosome entry site, immediately upstream of the translation initiation site, is indicated from the complementarity of a 12 nucleotide sequence with a region in the rat 18S rRNA. Chimeric constructs encompassing the region surrounding the transcription start site (-77-+171), as well as constructs with additional 1.9 kb upstream from this region revealed strong transcriptional activity when ligated to a luciferase reporter gene and tested in transient transfection assays. This activity was lost on deletion of the 5'-flanking region to -77. In addition, transcriptional activity was progressively lost with the inclusion of downstream sequences extending into the 5'-UTR. Several known response elements for proteins such as Runx2, NFkappaB, Smads, Sp1, and Ets1 are retained within the conserved sequences of rat and mouse AJ18, which was retrieved from mouse genomic libraries. Interestingly, the transcriptional activity was approximately 100-fold higher in the osteocarcinoma cell line ROS 2.8/17 compared to the fibroblast-like C3H10T1/2. Notably, this is the first gene promoter from the large KRAB/C(2)H(2) zinc finger family of proteins to be identified and characterized.
Jheon
Andrew H
AH
Department of Biochemistry, University of Toronto, Room 239 Fitzgerald Building, 150 College Street, Toronto, Ont. M5S 3E2, Canada. a.jheon@utoronto.ca
Suzuki
Naoto
N
Nishiyama
Takehisa
T
Cheifetz
Sela
S
Sodek
Jaro
J
Ganss
Bernhard
B
D024506:5' Flanking Region / Q000235:genetics*; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002478:Cells, Cultured; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins; D005091:Exons; D015870:Gene Expression; D005786:Gene Expression Regulation; D005796:Genes / Q000235:genetics; D006801:Humans; D007438:Introns; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics*; D024363:Transcription Initiation Site; D014158:Transcription, Genetic / Q000235:genetics; D014162:Transfection; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C485805:ZNF354C protein, human; C408086:Zfp354c protein, mouse; C485806:Zfp354c protein, rat; D008156:Luciferases