Genomic organization of the JEM-1 (BLZF1) gene on human chromosome 1q24: molecular cloning and analysis of its promoter region.
The Jem-1 (JEM-1, HGMW-approved symbol BLZF1) gene mapping to human chromosome 1q24 codes for a ubiquitously expressed 3-kb mRNA, translated in a 45-kDa nuclear protein. Recent studies have shown a deficient expression of this gene in acute promyelocytic leukemia (APL). However, treatment with retinoids was able to upregulate JEM-1 mRNA in maturing NB4 leukemia cells. Here, we report the characterization of the structural organization of JEM-1. By hybridization screening of a human genomic library derived from blood mononuclear cells, five overlapping genomic DNA clones were isolated. These clones extend over 34 kb of the human genome and comprise the complete JEM-1 gene and a 4-kb 5'flanking region. Determination of the exon-intron structure of Jem-1 revealed seven exons whose junctions with introns exhibited typical splice sequences. A shorter transcript (Jem-1s, 1.3 kb) generated by exon 3 extension and polyadenylation was identified. Its translation generated a 23-kDa protein that exhibited a cytoplasmic localization. 5'RACE-PCR identified a major transcription start site (TSS) located at 403 nt upstream of the ATG. Computer analysis of the 1. 8-kb 5'flanking region showed that it lacks a TATA box, Inr motifs or DPE motifs, but it contains a typical CCAAT box located 95 bp upstream of the TSS. Sequencing also revealed potential cis-acting elements for multiple transcription regulators including Sp1, GATA, C/EBP, AP-1, and Pu1. No retinoic acid receptor elements or retinoic X receptor elements were detected. This 1.8-kb DNA sequence showed a strong constitutive promoter activity determined by a luciferase-reporter gene assay in transiently transfected HeLa cells. Retinoids further increased luciferase expression 2.7-fold. We demonstrated that the 1-kb distal sequence contains yet unidentified elements reducing constitutive transcription. Thus, the maximal constitutive promoter activity was assigned to a -432 + 101 region overlapping the TSS. These data support the idea of a constitutive expression of JEM-1, but a negative regulation in APL released by retinoids.
Tong
J H
JH
Centre G. Hayem, I.N.S.E.R.M. U-496, Hôpital Saint-Louis, 1, Avenue Claude Vellefaux, Paris, 75010, France.
Fant
X
X
Benoit
G
G
Chen
S J
SJ
Chen
Z
Z
Lanotte
M
M
D020121:5' Untranslated Regions / Q000032:analysis; D000818:Animals; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D001665:Binding Sites; D019556:COS Cells; D002874:Chromosome Mapping; D002878:Chromosomes, Human, Pair 1; D003001:Cloning, Molecular; D018076:DNA, Complementary; D001330:Electronic Data Processing; D005091:Exons; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics*; D011061:Poly A; D011401:Promoter Regions, Genetic / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014162:Transfection
D020121:5' Untranslated Regions; C105528:BLZF1 protein, human; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D018076:DNA, Complementary; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D011061:Poly A