title: Promoter region of the transcriptional unit for human alpha 1-chimaerin, a neuron-specific GTPase-activating protein for p21rac.
abstract: alpha 1-chimaerin is a neuron-specific GTPase-activating protein for p21rac, a protein involved in morphological events. The mRNA is highly expressed in certain brain regions. It is also detected in cultured neuronal, but not in non-neuronal cells. As a first step towards understanding the mechanisms underlying this regulation, genomic clones containing the 5'-flanking region of the human alpha 1-chimaerin transcriptional unit were isolated and characterised. A cluster of multiple transcription start sites of alpha 1-chimaerin mRNAs was detected by primer-extension and S1-mapping analyses. The cluster was mapped to nucleotides -464 to -434 (relative to nucleotide A in the initiation codon) in genomic DNA. The 5'-proximal region contained no TATA box, initiator motif and Sp1-binding site. A 210-bp fragment with approximately 110 bp 5'-flanking sequence could function as a minimal promoter upon analysis using hybrid chloramphenicol acetyltransferase reporter constructs and transient transfection. Internal deletion and point-mutation experiments revealed that a GGCCAATC sequence located at nucleotides -519 to -512 was essential for alpha 1-chimaerin promoter activity. Mobility-shift assay showed the specific binding of nuclear factor(s) to this region, which was competed by the oligonucleotides corresponding to wild-type but not mutant forms. The data also suggest the existence of possible novel CCAAT-binding factor(s) interacting with the alpha 1-chimaerin CCAAT box binding site. A cell-type-preferred suppressor located in the 5'-distal region was found which may play a role in controlling neuron-specific expression of alpha 1-chimaerin mRNA. These findings of a specific promoter for alpha 1-chimaerin transcription will facilitate further studies on its neuronal-specific expression and function.
authors.affiliation: Glaxo/IMCB group, Institute of Molecular and Cell Biology, National University of Singapore.
authors.forename: J M
authors.initials: JM
authors.lastname: Dong
authors.forename: P
authors.initials: P
authors.lastname: Smith
authors.forename: C
authors.initials: C
authors.lastname: Hall
authors.forename: L
authors.initials: L
authors.lastname: Lim
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D020848:Chimerin 1; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D020690:GTPase-Activating Proteins; D015870:Gene Expression; D006801:Humans; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D020848:Chimerin 1; D017931:DNA Primers; D018076:DNA, Complementary; D020690:GTPase-Activating Proteins; D009419:Nerve Tissue Proteins; D011506:Proteins; D012333:RNA, Messenger