High impact information on CBP1

• To probe the relation between calcium limitation and intracellular parasitism, we designed a strategy to disrupt CBP1 in H. capsulatum using a telomeric linear plasmid and a two-step genetic selection [1].
• Identification and cloning of a yeast nuclear gene (CBP1) involved in expression of mitochondrial cytochrome b [2].
• A protein translated from the short transcripts was not detected by Western analysis, although polysome gradient fractions were shown to contain both long and short CBP1 transcripts [3].
• Having proposed that regulation of 3' end formation dictates the amount of each CBP1 transcript, we now show that a 146-bp fragment from the middle of CBP1 is sufficient to direct carbon source-regulated production of two transcripts when inserted into the yeast URA3 gene [4].
• This fragment contains seven polyadenylation sites for the wild-type 1.2-kb mRNA, as mapped by sequence analysis of CBP1 cDNA clones [4].

Biological context of CBP1

• Premature 3'-end formation of CBP1 mRNA results in the downregulation of cytochrome b mRNA during the induction of respiration in Saccharomyces cerevisiae [3].
• To test the idea that transcriptional regulation of CBP1 could coordinate an increase in cytochrome b mRNA stability with an increase in nuclearly encoded complex III subunit production, we characterized the change in abundance of CBP1 mRNA during derepression on a nonfermentable carbon source [5].
• The recombinant plasmid pG60/T10 with a nuclear DNA insert of 6.7 kilobase pairs (kb) was used to construct a new plasmid pool with the CBP1 gene on smaller fragments of nuclear DNA [6].
• Assembly of the mitochondrial membrane system. Nucleotide sequence of a yeast nuclear gene (CBP1) involved in 5' end processing of cytochrome b pre-mRNA [6].
• This phenotype mimics that of a mutation in the nuclear CBP1 gene [7].

Anatomical context of CBP1

• Assignment of Mr = 66,000 to the mature CBP1 polypeptide was verified by Western analysis of mitochondria from a strain which over-expresses CBP1 [8].
• Mitochondrial localization was verified by transcribing CBP1 in vitro with T3 polymerase, translating the artificial mRNA in a rabbit reticulocyte system and importing 35S-CBP1 precursor polypeptides into isolated mitochondria [8].
• We also evaluated CBP1 expression by reverse transcription-polymerase chain reaction (RT-PCR) of yeasts grown in broth culture and within two host cell types, a macrophage-like cell line and respiratory epithelial cells [9].

Associations of CBP1 with chemical compounds

• Poly(A)+ RNA from derepressed yeast cells was examined by Northern (RNA) analyses with cRNA probes from CBP1 [5].
• Fusion of a biotin binding peptide tag to the C terminus of Cbp1 has now allowed detection in mitochondrial extracts by using peroxidase-coupled avidin [10].

Physical interactions of CBP1

• CBP1 is a yeast nuclear gene encoding a mitochondrial protein that stabilizes the 5' end of cytochrome b (cob) pre-mRNA [5].

Regulatory relationships of CBP1

• In Saccharomyces cerevisiae, the nuclear-encoded protein Cbp1 promotes stability and translation of mitochondrial cytochrome b transcripts through interaction with the 5' untranslated region [10].

Other interactions of CBP1

• The presence of the oli1 leader sequence confers stability to the RNA and circumvents the CBP1 processing function [11].
• A hypothesis is presented in which the Cbp1-Pet309 complex contains several message-specific RNA binding proteins and links transcription to translation of the mRNAs at the membrane [10].

Analytical, diagnostic and therapeutic context of CBP1

• CBP1 was undetectable in a crude mitochondrial fraction from a wild-type strain by Western blot assay, but a 66-kDa immunoreactive protein was detected in a more purified fraction [8].
• Gel filtration analysis and blue native PAGE showed that Cbp1 is part of a single 900,000-Da complex [10].

References