Genomic and transcriptional linkage of the genes for calmodulin, EF-hand 5 protein, and ubiquitin extension protein 52 in Trypanosoma brucei.
We report genomic linkage of a pair of tandem, identical ubiquitin-extension protein 52 (EP52) genes, a novel EF-hand superfamily member gene (EFH5), and the calmodulin gene cluster in Trypanosoma brucei. The intergenic regions of these four genes are short: about 108 bp between the calmodulin gene C and the EFH5 gene, about 111 bp between the EFH5 gene and the ubiquitin-EP52/1 gene, and about 116 bp between the ubiquitin-EP52/1 and -EP52/2 genes. RNA molecules that span these three intergenic regions have been detected by polymerase chain reaction, which suggests that the genes are transcribed in a polycistronic manner. Transcription of the calmodulin, EFH5, and ubiquitin-EP52 genes in isolated nuclei is rapidly inactivated by UV irradiation, which further strengthens the hypothesis that this cluster of three different genes is transcribed in a polycistronic manner and suggests that they are under the control of a single distant upstream promoter. These results suggest that polycistronic transcription is common in trypanosomes and will probably be found for most, if not all, protein-encoding genes. The presence of at least three housekeeping genes with different known or potential regulatory functions within a polycistronic unit suggests that regulation of transcription initiation plays an important role in the coordinated expression of housekeeping genes in trypanosomes.
Department of Microbiology and Immunology, University of California, Los Angeles 90024.
S
S
Wong
T H
TH
Morales
J E
JE
Neigel
D A
DA
Campbell
D000546:Amanitins / Q000494:pharmacology; D000818:Animals; D001483:Base Sequence; D002135:Calcium-Binding Proteins / Q000235:genetics*; D002147:Calmodulin / Q000235:genetics*; D003001:Cloning, Molecular; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects; D017125:Genes, Protozoan; D008040:Genetic Linkage; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011401:Promoter Regions, Genetic; D011498:Protein Precursors / Q000235:genetics*; D015800:Protozoan Proteins / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D016053:RNA, Protozoan / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D015183:Restriction Mapping; D014158:Transcription, Genetic / Q000187:drug effects / Q000528:radiation effects; D014346:Trypanosoma brucei brucei / Q000235:genetics*; D014452:Ubiquitins / Q000235:genetics*; D014466:Ultraviolet Rays
D000546:Amanitins; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D009838:Oligodeoxyribonucleotides; D011498:Protein Precursors; D015800:Protozoan Proteins; D012333:RNA, Messenger; D016053:RNA, Protozoan; D014452:Ubiquitins; C045677:ubiquitin precursor; C075025:EFH5 protein, Trypanosoma brucei