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J Wuarin

Publications and source records attributed to J Wuarin.

8 recordsLinked to original sources
PubMed1997

Control of S-phase periodic transcription in the fission yeast mitotic cycle.

In fission yeast, passage through START and into S-phase requires cyclin-dependent kinase (CDK) activity and the periodic transcription of genes essential for S-phase ('S-phase transcription'). Here we investigate the control of this transcription in the mitotic cell cycle. We demonstrate that the periodicity of S-phase transcription is likely to be controlled independently of CDK activity. This contrasts with the equivalent system in budding yeast. Furthermore, the CDK function required for S-phase acts after the onset of S-phase transcription and after the accumulation of cdc18p, a critical target of this transcriptional machinery. We investigate the role of individual components of the S-phase transcriptional machinery, cdc10p, res1p, res2p and rep2p, and define a new role for res2p, previously demonstrated to be important in the meiotic cycle, in switching off S-phase transcription during G2 of the mitotic cycle. We show that the presence of the in vitro bandshift activity DSC1, conventionally thought to represent the active complex, requires res2p and correlates with inactive transcription. We suggest that S-phase transcription is controlled by both activation and repression, and that res2p represses transcription in G2 of the cell cycle as a part of the DSC1 complex.

CDC2 Protein Kinase↗
PubMed1994

Physical isolation of nascent RNA chains transcribed by RNA polymerase II: evidence for cotranscriptional splicing.

In order to examine whether splicing can occur cotranscriptionally in mammalian nuclei, we mapped exon-intron boundaries on nascent RNA chains transcribed by RNA polymerase II. A procedure that allows fractionation of nuclei into a chromatin pellet containing DNA, histones, and ternary transcription complexes and a supernatant containing the bulk of the nonhistone proteins and RNAs that are released from their DNA templates was developed. The transcripts of the genes encoding DBP, a transcriptional activator protein, and HMG coenzyme A reductase recovered from the chromatin pellet and the supernatant were analyzed by S1 nuclease mapping. The large majority of the RNA molecules from the pellet appeared to be nascent transcripts, since, in contrast to the transcripts present in the supernatant, they were not cleaved at the polyadenylation site but rather contained heterogeneous 3' termini encompassing this site. Splicing intermediates could be detected among nascent and released transcripts, suggesting that splicing occurs both cotranscriptionally and posttranscriptionally. Our results also indicate that polyadenylation is not required for the splicing of the last DBP intron. In addition to allowing detailed structural analysis of nascent RNA chains, the physical isolation of nascent transcripts also yields reliable measurements of relative transcription rates.

Animals↗
PubMed1992

The role of the transcriptional activator protein DBP in circadian liver gene expression.

DBP, a liver-enriched transcriptional activator protein of the leucine zipper protein family, accumulates according to a very strong circadian rhythm (amplitude approx. 1000-fold). In rat parenchymal hepatocytes, the protein is barely detectable during the morning hours. At about 2 p.m., DBP levels begin to rise, reach maximal levels at 8 p.m. and decline sharply during the night. This rhythm is free-running: it persists with regard to both its amplitude and phase in the absence of external time cues, such as daily dark/light switches. Also, fasting of rats for several days influences neither the amplitude nor the phase of circadian DBP expression. Since the levels of DBP mRNA and nascent transcripts also oscillate with a strong amplitude, circadian DBP expression is transcriptionally controlled. While DBP mRNA fluctuates with a similar phase and amplitude in most tissues examined, DBP protein accumulates to high concentrations only in liver nuclei. Hence, at least in nonhepatic tissues, cyclic DBP transcription is unlikely to be controlled by a positive and/or negative feedback mechanism involving DBP itself. More likely, the circadian DBP expression is governed by hormones whose peripheral concentrations also oscillate during the day. Several lines of evidence suggest a pivotal role of glucocorticoid hormones in establishing the DBP cycle. Two genes whose mRNAs and protein products accumulate according to a strong circadian rhythm with a phase compatible with regulation by DBP encode enzymes with key functions in cholesterol metabolism: HMG-coA reductase is the rate-limiting enzyme in cholesterol synthesis; cholesterol 7-alpha hydroxylase performs the rate-limiting step in the conversion of cholesterol to bile acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1990

Expression of the liver-enriched transcriptional activator protein DBP follows a stringent circadian rhythm.

The liver-enriched transcriptional activator protein DBP accumulates in hepatocytes of adult rats according to a strictly controlled circadian rhythm. DBP is not detectable in liver nuclei during the morning hours. Its level raises sharply during the afternoon and reaches a maximum at about 8 p.m. During the night the cellular DBP concentration decreases below detectability. This oscillation is "free running," transcriptionally regulated, and may be under the negative control of glucocorticoid hormones. In keeping with the rhythmicity of DBP accumulation, the albumin gene, a putative target of DBP, is transcribed more efficiently in the evening than in the morning.

Animals↗
PubMed1990

A ubiquitous CCAAT factor is required for efficient in vitro transcription from the mouse albumin promoter.

Among the various factors binding to DNA elements within the mouse albumin promoter, NF-Y is the only one present at identical concentrations in the nuclei of all examined tissues. NF-Y binds to albumin promoter element C, which contains the sequence CCAAT. To determine whether this factor augments in vitro transcription from the albumin promoter, an extensive point-mutation analysis was performed within the promoter element C. In liver extracts, six out of the ten mutations result in a strong inhibition of NF-Y binding and in a concomitant decrease in promoter activity. Two mutations that increase the affinity of the C-element for NF-Y also augment the transcription efficiency from the albumin promoter. A similarly strong correlation of NF-Y-binding with transcription efficiency has also been observed in spleen nuclear extracts. The liver-enriched CCAAT and enhancer binding factor C/EBP also recognizes the C element. In contrast to NF-Y, no correlation between the affinity of mutant C-elements for C/EBP and transcriptional activity could be observed in liver nuclear extracts.

Animals↗
PubMed1989

The role of cis-acting promoter elements in tissue-specific albumin gene expression.

The mouse albumin gene promoter has six closely spaced binding sites for nuclear proteins that are located between the TATA motif and nucleotide position -170. In vitro transcription with liver or spleen nuclear extracts of templates containing either mutated or polymerized albumin promoter elements establishes a hierarchy of the different protein binding sites for tissue-specific albumin gene transcription. The HNF-1 and C/EBP binding sites strongly activate transcription in a tissue-specific manner. The NF-Y binding site has a lower activation potential and is less specific, being equally efficient in liver and spleen nuclear extracts. The remaining elements are relatively weak activator sites.

Animals↗
PubMed1987

The interplay of DNA-binding proteins on the promoter of the mouse albumin gene.

The promoter of the mouse albumin gene contains at least six binding sites for specific DNA-binding proteins (A to F). Four of these sites (A, D, E, and F) can be occupied by transcription factors that are considerably enriched in liver nuclei, as compared to spleen or brain nuclei. These factors consist of a heat-stable protein that fills sites A, D, and F, and a member of a family of nuclear factor I (NF-I) related proteins that occupies site E. Site C binds a protein that is equally abundant in liver, brain, and spleen nuclei. Occupancy of this site and the binding of the heat-stable factor to the immediately adjacent site D appear to be mutually exclusive. However, both of these competing binding sites are required for maximal in vitro transcription.

Albumins↗