Mitochondrial DNA synthesis and the mitotic cycle in Physarum polycephalum

Güttes, E.; Hanawalt, Philip C.; Guttes, Sophie

doi:10.1016/0005-2787(67)90526-6

Cited by 91 publications

(22 citation statements)

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“…Heavy labeling during late interphase of a few nuclei which were above average in size has been observed previously (14) . The origin of these nuclei is at present unknown .…”

Section: Resultssupporting

confidence: 72%

“…Sachsenmaier (32) observed a slow, continuous increase of the amount of total DNA during the second half of the intermitotic period, which he interpreted as being due to cytoplasmic DNA synthesis . More recently, incorporation of thymidine-3H into a nuclear DNA fraction of higher density than the principal DNA (4,14) has been found during the S phase (3) as well as during the latter half (3, 17) of the intermitotic period . Our own experiments show two types of nuclear labeling in pulse experiments during the latter part of the intermitotic period .…”

Section: Resultsmentioning

confidence: 99%

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REPLICATION OF NUCLEOLUS-ASSOCIATED DNA DURING "G2 PHASE" IN PHYSARUM POLYCEPHALUM

Güttes

Guttes

1969

The Journal of Cell Biology

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In the myxomycete, Physarum polycephalum, the bulk of nuclear DNA replication occurs during a period of a few hours immediately following upon mitosis . During the remainder of the intermitotic period, incorporation of thymidine-3 H continues at a low rate in the region of the nucleolus (radioautographs) . A few nuclei incorporated thymidine-3 H into the extranucleolar chromatin at a high rate at all times of the intermitotic period . These nuclei were exceptionally large and they frequently contained several small nucleoli of different sizes rather than the one, central nucleolus which is characteristic of a normal interphase nucleus .

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“…Heavy labeling during late interphase of a few nuclei which were above average in size has been observed previously (14) . The origin of these nuclei is at present unknown .…”

Section: Resultssupporting

confidence: 72%

Section: Resultsmentioning

confidence: 99%

REPLICATION OF NUCLEOLUS-ASSOCIATED DNA DURING "G2 PHASE" IN PHYSARUM POLYCEPHALUM

Güttes

Guttes

1969

The Journal of Cell Biology

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“…P. polycephalum is a multinucleated organism and as many as 10 s nuclei may share the same cytoplasmic environment in a given plasmodium (15). The nuclei have no measurable G1 phase, and incubation of plasmodia with thymidine-3H for short periods of time immediately after mitosis or during the first 3 hr after mitosis results in heavy labeling of all nuclei (2,16). During the transition period between very early and very late interphase the number of nuclei incorporating thymidine-3H declines gradually (2), and heavily labeled and unlabeled nuclei may be found side by side.…”

Section: >99mentioning

confidence: 99%

REGULATION OF DNA REPLICATION IN THE NUCLEI OF THE SLIME MOLD PHYSARUM POLYCEPHALUM

Guttes

Güttes

1968

The Journal of Cell Biology

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Nuclei in G2 phase of the slime mold Physarum polycephalum, when transplanted, by plasmodial coalescence, into an S-phase plasmodium, failed to start another round of DNA synthesis. In the reciprocal combination, S-phase nuclei in a G2-phase host continued DNA synthesis for several hours without appreciable decrease in rate. It is suggested that the beginning of DNA replication is determined by an event, either during or shortly after mitosis, which renders the chromosomes structurally competent for DNA replication.

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“…An unusual feature of DNA replication in trypanosomes is that both kinetoplast and nuclear DNA replicate in approximate synchrony (4,5). In other eukaryotes, mitochondrial DNA replication occurs throughout the cell cycle (6,7). Since both the kinetoplast and nuclear DNA replication genes are encoded in the nucleus, their coordinated expression may play a role in synchronizing nuclear and kDNA replication.…”

mentioning

confidence: 99%

Nulear Extracts of Crithidia fasciculata Contain a Factor(s) That Binds to the 5′-Untranslated Regions of TOP2 and RPA1 mRNAs Containing Sequences Required for Their Cell Cycle Regulation

Mahmood

1998

Journal of Biological Chemistry

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The Crithidia fasciculata replication protein A gene, RPA1, and topoisomerase II gene, TOP2, encode proteins involved in the replication of nuclear and mitochondrial DNA, respectively. Transcripts of both genes accumulate periodically during the cell cycle and attain their maximum levels just before S phase. Octamer consensus sequences within the 5-untranslated region (UTR) of both genes have been shown to be necessary for cycling of these transcripts. Using a gel retardation assay, we show here that nuclear extracts of C. fasciculata contain a protein factor(s) that binds specifically to RNA from 5-UTRs of TOP2 and RPA1 genes. In addition, mutations in the consensus octamer sequence abolish binding to the RNA in both cases. Ultraviolet cross-linking using a radiolabeled TOP2 5-UTR probe identified proteins with apparent molecular masses of 74 and 37 kDa in the RNA-protein complex. Nuclear extracts prepared from synchronized cells show that the binding activity varies during the cell cycle in parallel with TOP2 and RPA1 mRNA levels. These results suggest that the cell cycle regulation of the mRNA levels of trypanosomatid DNA replication genes may be mediated by binding of specific proteins to conserved sequences in the 5-UTR of their transcripts.The trypanosomatid Crithidia fasciculata is a protozoan parasite containing a single mitochondrion with an unusual form of DNA called kinetoplast DNA (kDNA) 1 (1, 2). The kDNA consists of a single network of catenated minicircles and maxicircles. During replication of kDNA, the minicircles are released from the network and are reattached to the network periphery after replication, whereas maxicircles replicate while still attached to the network (3). An unusual feature of DNA replication in trypanosomes is that both kinetoplast and nuclear DNA replicate in approximate synchrony (4, 5). In other eukaryotes, mitochondrial DNA replication occurs throughout the cell cycle (6, 7). Since both the kinetoplast and nuclear DNA replication genes are encoded in the nucleus, their coordinated expression may play a role in synchronizing nuclear and kDNA replication.Expression of protein-coding genes in trypanosomatids involves mechanisms that are different from those in most other eukaryotes. All mRNAs in trypanosomatids contain two exons, a 39-nucleotide miniexon at the 5Ј end of the mRNA and the main coding exon (8, 9). Genes are usually grouped in polycistronic transcription units, and the polycistronic pre-mRNAs are processed by 5Ј trans-splicing and 3Ј polyadenylation to yield monocistronic mRNAs. The differential expression of steady state mRNAs from a single polycistronic transcript involves post-transcriptional controls by mechanisms that are still unclear. Pre-mRNA turnover in combination with differential rates of trans-splicing and polyadenylation and of mRNA turnover may all play a role in regulating mRNA levels. So far, only two RNA polymerase II promoters for protein-coding genes have been described in trypanosomes, the Trypanosoma congolense glutamic acid/alanine-rich ...

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Mitochondrial DNA synthesis and the mitotic cycle in Physarum polycephalum

Cited by 91 publications

References 22 publications

REPLICATION OF NUCLEOLUS-ASSOCIATED DNA DURING "G2 PHASE" IN PHYSARUM POLYCEPHALUM

REPLICATION OF NUCLEOLUS-ASSOCIATED DNA DURING "G2 PHASE" IN PHYSARUM POLYCEPHALUM

REGULATION OF DNA REPLICATION IN THE NUCLEI OF THE SLIME MOLD PHYSARUM POLYCEPHALUM

Nulear Extracts of Crithidia fasciculata Contain a Factor(s) That Binds to the 5′-Untranslated Regions of TOP2 and RPA1 mRNAs Containing Sequences Required for Their Cell Cycle Regulation

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