Nuclear control of the expression of the cytochrome b gene in yeast mitochondrial DNA : (apocytochrome b gene, Saccharomyces cerevisiae, CBP1 gene)

The mitochondrial gene encoding apocytochrome b is mosaic, containing two intervening sequences in the Saccharomyces cerevisiae strain D273-10B. Five nuclear genes and one mitochondrial gene have been identified that are necessary for the correct processing of the mitochondrial apocytochrome b pre-messenger RNA. The apocytochrome b mRNA from the wild-type strain has been characterized by Northern blot analyses, S1 mapping of the 5' and 3' ends and reverse transcription of the exon/intron boundaries. Apocytochrome b pre-messenger RNA processing has been investigated by Northern blot analyses of RNA from the wild-type strain, mitochondrial mit[superscript -] and p[superscript -] mutant strains and nuclear respiratory deficient pet mutants. CBP1, a nuclear gene complementing one set of pet mutants defective in apocytochrome b mRNA processing, has been cloned and sequenced, revealing an open reading frame that could code for a basic protein of 76,000 daltons.Carol L . Dieckmann and Louise K. Pape, Department of Biological Sciences, Columbia University, New York , N.Y

Different opinion on the reported role of Poldip2 and ACSM1 in a mammalian lipoic acid salvage pathway controlling HIF-1 activation.

Paredes et al recently described Poldip2 as a novel regulator of mitochondrial lipoylation through stabilisation of ACSM1 (1). We have several concerns with their proposed model based on the following reasons.Wellcome 102770/Z/13/Z and 205252/Z/16/Z Lister Institute RG8795

The \u3cem\u3eChlamydomonas\u3c/em\u3e Genome Reveals the Evolution of Key Animal and Plant Functions

Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the ∼120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella

Analysis of transcription asymmetries along the tRNA(E)-COB operon: evidence for transcription attenuation and rapid RNA degradation between coding sequences

Mitochondrial gene expression in yeast is believed to be regulated predominantly at the post-transcriptional level. However, the contribution of mitochondrial transcription and RNA-turnover rates to differential gene regulation is still largely unknown. Mitochondrial run-on transcription and hybrid selection assays showed that some of the multigenic transcription units of the mitochondrial genome are transcribed evenly, whereas others are transcribed asymmetrically, with higher transcription rates for promoter-proximal genes, than for promoter-distal genes. The tRNA(E)-cytochrome b (COB) operon was analyzed in detail to investigate the mechanisms underlying transcription rate asymmetries in yeast mitochondria. We showed that a drop in transcription rates occurs in a particular region between the coding sequences and is independent of the coding sequence of the downstream COB gene. Deletion of the region between tRNA(E) and COB coding sequences decreases the drop in transcription rates. Deletion of the nuclear gene encoding the Pet 127 protein, which is involved in mitochondrial RNA 5′ processing and degradation, also partially relieves transcriptional asymmetry. Therefore, asymmetry is probably due to a combination of attenuated transcription at specific sites between the coding sequences and very rapid RNA degradation