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.
Wong
S
S
Department of Microbiology and Immunology, University of California, Los Angeles 90024.
Morales
T H
TH
Neigel
J E
JE
Campbell
D A
DA
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