Identification of nerve growth factor-responsive element of the TCL1 promoter as a novel negative regulatory element.
The serine/threonine kinase, Akt (protein kinase B) plays a central role in the regulation of intracellular cell survival. Recently, we demonstrated that the proto-oncogene TCL1, overexpressed in human T-cell prolymphocytic leukemia, is an Akt kinase co-activator. Tightly restricted TCL1 gene expression in early developmental cells suggested that the TCL1 gene is regulated at a transcriptional level. To characterize how TCL1 gene expression is regulated, we cloned the 5'-promoter of the TCL1 gene located at human chromosome 14q32. The 5'-TCL1 promoter region contains a TATA box with cis-regulatory elements for Nur77/NGFI-B (nerve growth factor-responsive element (NBRE), CCAAGGTCA), NFkappaB, and fork head transcription factor. Nur77/NGFI-B, an orphan receptor superfamily transcription factor implicated in T-cell apoptosis, is a substrate for Akt. We hypothesized that TCL1 transactivity is regulated through Akt-induced phosphorylation of Nur77/NGFI-B in vivo. In an electrophoretic mobility shift assay with chromosomal immunoprecipitation assays, wild-type Nur77, but not S350A mutant Nur77, could specifically bind to TCL1-NBRE. A luciferase assay demonstrated that TCL1-NBRE is required for inhibition of TCL1 transactivity upon nerve growth factor/platelet-derived growth factor stimulation, which activates Akt and phosphorylates Nur77. Using a chromosomal immunoprecipitation assay with reverse transcription-PCR, nerve growth factor stimulation inhibited binding of endogenous Nur77 to TCL1-NBRE, in turn, suppressing TCL1 gene expression. The results together establish that TCL1-NBRE is a novel negative regulatory element of Nur77 (NGFI-B). To the best of our knowledge, TCL1-NBRE is the first direct target of Nur77 involving the regulation of intracellular cell death survival. This Akt-induced inhibitory mechanism of TCL1 should play an important role in immunological and/or neuronal development in vivo.
Hiromura
Makoto
M
Division of Cancer Biology, Institute for Genetic Medicine, Hokkaido University, Sapporo 060-0815, Japan.
Suizu
Futoshi
F
Narita
Masumi
M
Kinowaki
Keiichi
K
Noguchi
Masayuki
M
D000818:Animals; D001483:Base Sequence; D004268:DNA-Binding Proteins / Q000378:metabolism; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors / Q000502:physiology; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D020932:Nerve Growth Factor / Q000494:pharmacology*; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D051057:Proto-Oncogene Proteins c-akt / Q000502:physiology; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011987:Receptors, Steroid / Q000378:metabolism; D020218:Response Elements / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism
D004268:DNA-Binding Proteins; C499517:FOXO3 protein, human; D000071316:Forkhead Box Protein O3; D051858:Forkhead Transcription Factors; C000715470:MAS1 protein, human; C539821:NR4A1 protein, human; C539818:Nr4a1 protein, mouse; C539820:Nr4a1 protein, rat; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D010982:Platelet-Derived Growth Factor; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; C090851:TCL1A protein, human; D014157:Transcription Factors; D020932:Nerve Growth Factor; D051057:Proto-Oncogene Proteins c-akt