PubMed Health⌕ Search

Biomedical subjects

E M Denovan-Wright

Publications and source records attributed to E M Denovan-Wright.

23 records · Page 2Linked to original sources
PubMed1995

Evidence that the fragmented ribosomal RNAs of Chlamydomonas mitochondria are associated with ribosomes.

The discontinuous and scrambled organization of the small subunit and large subunit rRNA coding regions in Chlamydomonas mitochondrial DNA has been well documented. Our goals were to demonstrate that the small transcripts produced by these coding regions in Chlamydomonas eugametos are assembled into mitochondrial ribosomes and to characterize the sedimentation properties of these ribosomes and their subunits in sucrose gradients. Putative mitochondrial ribosomes (60-66S) and their large (44-50S) and small (35-39S) subunits were identified by slot blot hybridization which sedimented independently of the chloroplast and cytosolic ribosomes. A crude mitochondrial pellet prepared from C. eugametos was enriched for mitochondrial small subunit and large subunit rRNA subfragments thereby providing independent confirmation of the mitochondrial association of these rRNA molecules.

Animals↗
PubMed1994

Comparative structure and genomic organization of the discontinuous mitochondrial ribosomal RNA genes of Chlamydomonas eugametos and Chlamydomonas reinhardtii.

We report that the mitochondrial ribosomal RNAs (rRNAs) of Chlamydomonas eugametos are discontinuously encoded in separate gene pieces that are scrambled in order and interspersed with protein coding genes. Individual transcripts of these mitochondrial rRNA gene pieces have the potential to form standard rRNA secondary structures through intermolecular base-pairing and they all have termini that are confined to previously defined variable rRNA domains. The C. eugametos and the previously described Chlamydomonas reinhardtii mitochondrial DNAs, therefore, share the unusual feature of highly fragmented and extensively rearranged rRNA coding regions, which contrasts with the conventional mitochondrial rRNA gene structure of land plants and other green algae. Although many of the sites of mitochondrial rRNA discontinuity are in corresponding variable regions in the two Chlamydomonas species, several variable rRNA regions are interrupted in one species but not the other and the 5' to 3' order of the C. eugametos and C. reinhardtii gene pieces is very different. Based on these results, we conclude that the last common ancestor of C. eugametos and C. reinhardtii had discontinuous mitochondrial rRNA genes and that processes responsible for the further division and scrambling of these coding regions have continued since the divergence of C. eugametos and C. reinhardtii. The presence of four group I introns within the C. eugametos mitochondrial rRNA gene pieces leads us to favour recombination rather than reverse-transcription as the mechanism giving rise to the scrambled arrangement of rRNA genes in Chlamydomonas mitochondria.

Animals↗
PubMed1992

Comparative analysis of the mitochondrial genomes of Chlamydomonas eugametos and Chlamydomonas moewusii.

We report the cloning and physical mapping of the mitochondrial genome of Chlamydomonas eugametos together with a comparison of the overall sequence structure of this DNA with the mitochondrial genome of Chlamydomonas moewusii, its closely related and interfertile relative. The C. eugametos mitochondrial DNA (mtDNA) has a 24 kb circular map and is thus 2 kb larger than the 22 kb circular mitochondrial genome of C. moewusii. Restriction mapping and heterologous, fragment hybridization experiments indicate that the C. eugametos and C. moewusii mtDNAs are colinear. Nine cross-hybridizing restriction fragments common to the C. eugametos and C. moewusii mtDNAs, and spanning the entirely of these genomes, show length differences between homologous fragments which vary from 0.1 to 2.3 kb. A 600 bp subfragment of C. moewusii mtDNA, within one of these conserved fragments, showed no hybridization with the C. eugametos mtDNA. Of the 73 restriction sites identified in the C. eugametos and C. moewusii mtDNAs, five are specific to C. moewusii, eight are specific to C. eugametos and 30 are common to both species. Hybridization experiments with gene probes derived from protein-coding and ribosomal RNA-coding regions of wheat and Chlamydomonas reinhardtii mtDNAs support the view that the small and large subunit ribosomal RNA-coding regions of the C. eugametos and C. moewusii mtDNAs are interrupted and interspersed with each other and with protein-coding regions, as are the ribosomal RNA-coding regions of C. reinhardtii mtDNA; however, the specific arrangement of these coding elements in the C. eugametos and C. moewusii mtDNAs appears different from that of C. reinhardtii mtDNA.

Animals↗
PubMed1991

Immunologically-related nucleic acid-binding proteins associated with the nuclear matrix of Physarum polycephalum.

The nuclear matrix of Physarum polycephalum is composed of two abundant polypeptides of 27 and 38 kDa as well as numerous minor polypeptides of various molecular weight. By contrast, the nuclear matrix of vertebrates consists of three major (the lamins) and many minor polypeptides mainly in the 60-70 kDa molecular weight range. In order to better characterize the major nuclear matrix proteins of P. polycephalum and, perhaps, define their relationship with the major nuclear matrix proteins of vertebrates, we have purified the abundant nuclear matrix proteins of P. polycephalum. In Western blot analyses, polyclonal antibodies raised against the purified 27 kDa polypeptide recognised polypeptides of 50 kDa, 45 kDa and several low molecular weight species (14-21 kDa) in the P. polycephalum nuclear matrix. The polyclonal antibodies did not react with the other abundant nuclear matrix protein of 38 kDa from P. polycephalum nor with polypeptides of the mouse nuclear matrix. Two-dimensional gel electrophoresis showed that the major nuclear matrix proteins of P. polycephalum were more basic than the major nuclear matrix proteins of vertebrates, the lamins. Moreover, both the 27 and 38 kDa polypeptides are post-translationally modified by either D-mannosyl or D-glycosyl moieties, and not by phosphorylation as has been demonstrated for the vertebrate lamins. DNA-binding assays further revealed that the immunologically related polypeptides of 50 kDa, 45 kDa, 27 kDa and low molecular weight species of 14-21 kDa preferentially bound single-stranded DNA, but the 38 kDa polypeptide of Physarum matrix did not. Based on these findings, we conclude that the abundant nuclear matrix protein of 27 kDa belongs to a group of immunologically-related nucleic acid-binding proteins, and is immunologically and functionally distinct from the other major nuclear matrix protein of 38 kDa from P. polycephalum and the vertebrate lamins.

Autoradiography↗