Role of interactions between the origin recognition complex and SIR1 in transcriptional silencing

Nature ◽  
1996 ◽  
Vol 381 (6579) ◽  
pp. 251-253 ◽  
Author(s):  
Thomas Triolo ◽  
Rolf Sternglanz
Keyword(s):  
Origin Recognition Complex ◽  
Transcriptional Silencing ◽  
Origin Recognition

scholarly journals The role of ATP in the function of human ORC4 protein

2010 ◽  
Vol 75 (3) ◽  
pp. 317-322
Author(s):  
Aleksandra Divac ◽  
Branko Tomic ◽  
Jelena Kusic
Keyword(s):  
Conformational Changes ◽  
Origin Recognition Complex ◽  
Structural Changes ◽  
Atp Hydrolysis ◽  
Protein A ◽  
Structural Role ◽  
A Subunit ◽  
Dna Substrates ◽  
Origin Recognition

Human ORC4 protein, a subunit of the origin recognition complex, belongs to the AAA+ superfamily of ATPases. Proteins belonging to this family require ATP for their function and interactions with ATP lead to conformational changes in them or in their partners. Human ORC4 protein induces structural changes in DNA substrates, promoting renaturation and formation of non-canonical structures, as well as conversion of single-stranded into multi-stranded oligonucleotide structures. The aim of this study was to further investigate the role of ATP in the function of human ORC4 protein. For this purpose, a mutant in the conserved Walker B motif of ORC4, which is able to bind but not to hydrolyze ATP, was constructed and its activity in DNA restructuring reactions was investigated. The obtained results showed that ATP hydrolysis is not necessary for the function of human ORC4. It is proposed that ATP has a structural role as a cofactor in the function of human ORC4 as a DNA restructuring agent.

Analysis of mutant origin recognition complex with reduced ATPase activity in vivo and in vitro

2008 ◽  
Vol 413 (3) ◽  
pp. 535-543 ◽  
Author(s):  
Masaya Takehara ◽  
Masaki Makise ◽  
Hitomi Takenaka ◽  
Teita Asano ◽  
Tohru Mizushima
Keyword(s):  
Atpase Activity ◽  
Origin Recognition Complex ◽  
S Phase ◽  
Yeast Cells ◽  
Chromosomal Dna ◽  
Aaa Atpases ◽  
Origin Recognition

In eukaryotes, ORC (origin recognition complex), a six-protein complex, is the most likely initiator of chromosomal DNA replication. ORC belongs to the AAA+ (ATPases associated with a variety of cellular activities) family of proteins and has intrinsic ATPase activity derived from Orc1p, one of its subunits. To reveal the role of this ATPase activity in Saccharomyces cerevisiae (baker's yeast) ORC, we mutated the Orc1p sensor 1 and sensor 2 regions, which are important for ATPase activity in AAA+ proteins. Plasmid-shuffling analysis revealed that Asn600, Arg694 and Arg704 are essential for the function of Orc1p. In yeast cells, overexpression of Orc1R694Ep inhibited growth, caused inefficient loading of MCM (mini-chromosome maintenance complex of proteins) and slowed the progression of S phase. In vitro, purified ORC-1R [ORC with Orc1R694Ep (Orc1p Arg694→Glu mutant)] has decreased ATPase activity in the presence or absence of origin DNA. However, other activities (ATP binding and origin DNA binding) were indistinguishable from those of wild-type ORC. The present study showed that Arg694 of the Orc1p subunit is important for the ATPase activity of ORC and suggests that this ATPase activity is required for efficient MCM loading on to origin DNA and for progression of S phase.

scholarly journals Distinct Cytoplasmic and Nuclear Fractions of Drosophila Heterochromatin Protein 1: Their Phosphorylation Levels and Associations with Origin Recognition Complex Proteins

1998 ◽  
Vol 142 (2) ◽  
pp. 307-318 ◽  
Author(s):  
Da Wei Huang ◽  
Laura Fanti ◽  
Daniel T.S. Pak ◽  
Michael R. Botchan ◽  
Sergio Pimpinelli ◽  
...  
Keyword(s):  
Origin Recognition Complex ◽  
Binding Activity ◽  
Heterochromatin Protein 1 ◽  
Dna Binding Activity ◽  
Nucleation Sites ◽  
Repressive Effect ◽  
Drosophila Heterochromatin ◽  
Drosophila Heterochromatin Protein ◽  
Origin Recognition

The distinct structural properties of heterochromatin accommodate a diverse group of vital chromosome functions, yet we have only rudimentary molecular details of its structure. A powerful tool in the analyses of its structure in Drosophila has been a group of mutations that reverse the repressive effect of heterochromatin on the expression of a gene placed next to it ectopically. Several genes from this group are known to encode proteins enriched in heterochromatin. The best characterized of these is the heterochromatin-associated protein, HP1. HP1 has no known DNA-binding activity, hence its incorporation into heterochromatin is likely to be dependent upon other proteins. To examine HP1 interacting proteins, we isolated three distinct oligomeric species of HP1 from the cytoplasm of early Drosophila embryos and analyzed their compositions. The two larger oligomers share two properties with the fraction of HP1 that is most tightly associated with the chromatin of interphase nuclei: an underphosphorylated HP1 isoform profile and an association with subunits of the origin recognition complex (ORC). We also found that HP1 localization into heterochromatin is disrupted in mutants for the ORC2 subunit. These findings support a role for the ORC-containing oligomers in localizing HP1 into Drosophila heterochromatin that is strikingly similar to the role of ORC in recruiting the Sir1 protein to silencing nucleation sites in Saccharomyces cerevisiae.

The Role of Sas2, an Acetyltransferase Homologue of Saccharomyces cerevisiae, in Silencing and ORC Function

Genetics ◽  
1997 ◽  
Vol 145 (4) ◽  
pp. 923-934 ◽  
Author(s):  
Ann E Ehrenhofer-Murray ◽  
David H Rivier ◽  
Jasper Rine
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Binding Sites ◽  
Origin Recognition Complex ◽  
Consensus Sequence ◽  
Opposing Effects ◽  
Regulatory Sites ◽  
Origin Recognition

Silencing at the cryptic mating-type loci HML and HMR of Saccharomyces cerevisiae requires regulatory sites called silencers. Mutations in the Rap1 and Abf1 binding sites of the HMR-E silencer (HMR  a-e**) cause the silencer to be nonfunctional, and hence, cause derepression of HMR. Here, we have isolated and characterized mutations in SAS2 as second-site suppressors of the silencing defect of HMR  a-e**. Silencing conferred by the removal of SAS2 (sas2Δ) depended upon the integrity of the ARS consensus sequence of the HMR-E silencer, thus arguing for an involvement of the origin recognition complex (ORC). Restoration of silencing by sas2Δ required ORC2 and ORC5, but not SIR1 or RAP1. Furthermore, sas2Δ suppressed the·temperature sensitivity, but not the silencing defect of orc2-1 and orc5-1. Moreover, sas2Δ had opposing effects on silencing of HML and HMR. The putative Sas2 protein bears similarities to known protein acetyltransferases. Several models for the role of Sas2 in silencing are discussed.

Origin recognition complex (ORC) in transcriptional silencing and DNA replication in S. cerevisiae

Science ◽  
1993 ◽  
Vol 262 (5141) ◽  
pp. 1838-1844 ◽  
Author(s):  
M Foss ◽  
F. McNally ◽  
P Laurenson ◽  
J Rine
Keyword(s):  
Dna Replication ◽  
Origin Recognition Complex ◽  
Transcriptional Silencing ◽  
Origin Recognition

scholarly journals A Role for the Replication Proteins PCNA, RF-C, Polymerase ε and Cdc45 in Transcriptional Silencing in Saccharomyces cerevisiae

Genetics ◽  
1999 ◽  
Vol 153 (3) ◽  
pp. 1171-1182
Author(s):  
Ann E Ehrenhofer-Murray ◽  
Rohinton T Kamakaka ◽  
Jasper Rine
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Origin Recognition Complex ◽  
Transcriptional Silencing ◽  
Replication Timing ◽  
Replication Proteins ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cycle Progression

Abstract Transcriptional silencing in the budding yeast Saccharomyces cerevisiae may be linked to DNA replication and cell cycle progression. In this study, we have surveyed the effect of 41 mutations in genes with a role in replication, the cell cycle, and DNA repair on silencing at HMR. Mutations in PCNA (POL30), RF-C (CDC44), polymerase ε (POL2, DPB2, DPB11), and CDC45 were found to restore silencing at a mutant HMR silencer allele that was still a chromosomal origin of replication. Replication timing experiments indicated that the mutant HMR locus was replicated late in S-phase, at the same time as wild-type HMR. Restoration of silencing by PCNA and CDC45 mutations required the origin recognition complex binding site of the HMR-E silencer. Several models for the precise role of these replication proteins in silencing are discussed.

scholarly journals Origin Recognition Complex (ORC) Evolution Is Influenced by Global Gene Duplication/Loss Patterns in Eukaryotic Genomes

2020 ◽  
Vol 12 (2) ◽  
pp. 3878-3889 ◽  
Author(s):  
Eduard Ocaña-Pallarès ◽  
Zaida Vergara ◽  
Bénédicte Desvoyes ◽  
Manuel Tejada-Jimenez ◽  
Ainoa Romero-Jurado ◽  
...  
Keyword(s):  
Evolutionary History ◽  
Origin Recognition Complex ◽  
Free Living ◽  
Data Set ◽  
Genome Duplications ◽  
History Of ◽  
Eukaryotic Genomes ◽  
Eukaryotic Feature ◽  
Origin Recognition

Abstract The conservation of orthologs of most subunits of the origin recognition complex (ORC) has served to propose that the whole complex is common to all eukaryotes. However, various uncertainties have arisen concerning ORC subunit composition in a variety of lineages. Also, it is unclear whether the ancestral diversification of ORC in eukaryotes was accompanied by the neofunctionalization of some subunits, for example, role of ORC1 in centriole homeostasis. We have addressed these questions by reconstructing the distribution and evolutionary history of ORC1-5/CDC6 in a taxon-rich eukaryotic data set. First, we identified ORC subunits previously undetected in divergent lineages, which allowed us to propose a series of parsimonious scenarios for the origin of this multiprotein complex. Contrary to previous expectations, we found a global tendency in eukaryotes to increase or decrease the number of subunits as a consequence of genome duplications or streamlining, respectively. Interestingly, parasites show significantly lower number of subunits than free-living eukaryotes, especially those with the lowest genome size and gene content metrics. We also investigated the evolutionary origin of the ORC1 role in centriole homeostasis mediated by the PACT region in human cells. In particular, we tested the consequences of reducing ORC1 levels in the centriole-containing green alga Chlamydomonas reinhardtii. We found that the proportion of centrioles to flagella and nuclei was not dramatically affected. This, together with the PACT region not being significantly more conserved in centriole-bearing eukaryotes, supports the notion that this neofunctionalization of ORC1 would be a recent acquisition rather than an ancestral eukaryotic feature.

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