scholarly journals Different Residues on the Surface of theMethanothermobacter thermautotrophicusMCM Helicase Interact with Single- and Double-Stranded DNA

Archaea ◽  
2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Nozomi Sakakibara ◽  
Rajesh Kasiviswanathan ◽  
Zvi Kelman
Keyword(s):  
Opposite Effect ◽  
Chromosomal Dna ◽  
Minichromosome Maintenance ◽  
Conserved Residues ◽  
Replicative Helicase ◽  
Double Stranded Dna ◽  
Archaeal Species ◽  
Mcm Complex ◽  
Protein Multimerization ◽  
Conserved Amino Acids

The minichromosome maintenance (MCM) complex is thought to function as the replicative helicase in archaea, separating the two strands of chromosomal DNA during replication. The catalytic activity resides within the C-terminal region of the MCM protein, while the N-terminal portion plays an important role in DNA binding and protein multimerization. An alignment of MCM homologues from several archaeal species revealed a number of conserved amino acids. Here several of the conserved residues located on the surface of the helicase have been mutated and their roles in MCM functions determined. It was found that some mutations result in increased affinity for ssDNA while the affinity for dsDNA is decreased. Other mutants exhibit the opposite effect. Thus, the data suggest that these conserved surface residues may participate in MCM-DNA interactions.

scholarly journals Unwinding 20 Years of the Archaeal Minichromosome Maintenance Helicase

2020 ◽  
Vol 202 (6) ◽  
Author(s):  
Lori M. Kelman ◽  
William B. O’Dell ◽  
Zvi Kelman
Keyword(s):  
Dna Replication ◽  
Replication Fork ◽  
Duplex Dna ◽  
Chromosomal Dna ◽  
Minichromosome Maintenance ◽  
Replicative Helicase ◽  
Dna Helicases ◽  
First Report ◽  
20Th Anniversary

ABSTRACT Replicative DNA helicases are essential cellular enzymes that unwind duplex DNA in front of the replication fork during chromosomal DNA replication. Replicative helicases were discovered, beginning in the 1970s, in bacteria, bacteriophages, viruses, and eukarya, and, in the mid-1990s, in archaea. This year marks the 20th anniversary of the first report on the archaeal replicative helicase, the minichromosome maintenance (MCM) protein. This minireview summarizes 2 decades of work on the archaeal MCM.

The MCM complex: (just) a replicative helicase?

2008 ◽  
Vol 36 (1) ◽  
pp. 136-140 ◽  
Author(s):  
Alessandro Costa ◽  
Silvia Onesti
Keyword(s):  
Minichromosome Maintenance ◽  
Replicative Helicase ◽  
Aaa Atpase ◽  
Mcm Helicase ◽  
Eukaryotic Dna ◽  
Mcm Complex ◽  
Elongation Step ◽  
Hexameric Helicases

The MCM2–MCM7 (minichromosome maintenance 2–7) complex is involved both in the initiation and the elongation step of eukaryotic DNA replication and is believed to be the replicative helicase. Whereas the mechanism of DNA unwinding at the replication fork has been extensively investigated, the role of the MCM2–MCM7 complex during initiation has not yet been characterized by biochemical studies. Here we summarize the in vivo evidence which supports a role for the MCM complex in origin melting. In addition, we present an overview of the mechanism of action of a number of AAA+ (ATPase associated with various cellular activities) initiators and hexameric helicases, which can be used in turn as models for the steps of recognition, duplex melting, loading and nucleic acid translocation of the MCM helicase.

Structure and function of the GINS complex, a key component of the eukaryotic replisome

2010 ◽  
Vol 425 (3) ◽  
pp. 489-500 ◽  
Author(s):  
Stuart A. MacNeill
Keyword(s):  
Replication Fork ◽  
Biochemical Analysis ◽  
Current Knowledge ◽  
Chromosomal Dna ◽  
Minichromosome Maintenance ◽  
Replication Process ◽  
Replicative Helicase ◽  
Cellular Life ◽  
Mcm Helicase ◽  
And Function

High-fidelity chromosomal DNA replication is fundamental to all forms of cellular life and requires the complex interplay of a wide variety of essential and non-essential protein factors in a spatially and temporally co-ordinated manner. In eukaryotes, the GINS complex (from the Japanese go-ichi-ni-san meaning 5-1-2-3, after the four related subunits of the complex Sld5, Psf1, Psf2 and Psf3) was recently identified as a novel factor essential for both the initiation and elongation stages of the replication process. Biochemical analysis has placed GINS at the heart of the eukaryotic replication apparatus as a component of the CMG [Cdc45–MCM (minichromosome maintenance) helicase–GINS] complex that most likely serves as the replicative helicase, unwinding duplex DNA ahead of the moving replication fork. GINS homologues are found in the archaea and have been shown to interact directly with the MCM helicase and with primase, suggesting a central role for the complex in archaeal chromosome replication also. The present review summarizes current knowledge of the structure, function and evolution of the GINS complex in eukaryotes and archaea, discusses possible functions of the GINS complex and highlights recent results that point to possible regulation of GINS function in response to DNA damage.

scholarly journals Rif1 regulates telomere length through conserved HEAT repeats

2021 ◽  
Vol 49 (7) ◽  
pp. 3967-3980
Author(s):  
Calla B Shubin ◽  
Rini Mayangsari ◽  
Ariel D Swett ◽  
Carol W Greider
Keyword(s):  
Dna Binding ◽  
Telomere Length ◽  
Functional Role ◽  
Conserved Residues ◽  
Binding Interface ◽  
Binding Function ◽  
Length Regulation ◽  
Telomere Length Regulation ◽  
Telomere Regulation ◽  
Conserved Amino Acids

AbstractIn budding yeast, Rif1 negatively regulates telomere length, but the mechanism of this regulation has remained elusive. Previous work identified several functional domains of Rif1, but none of these has been shown to mediate telomere length. To define Rif1 domains responsible for telomere regulation, we localized truncations of Rif1 to a single specific telomere and measured telomere length of that telomere compared to bulk telomeres. We found that a domain in the N-terminus containing HEAT repeats, Rif1177–996, was sufficient for length regulation when tethered to the telomere. Charged residues in this region were previously proposed to mediate DNA binding. We found that mutation of these residues disrupted telomere length regulation even when Rif1 was tethered to the telomere. Mutation of other conserved residues in this region, which were not predicted to interact with DNA, also disrupted telomere length maintenance, while mutation of conserved residues distal to this region did not. Our data suggest that conserved amino acids in the region from 436 to 577 play a functional role in telomere length regulation, which is separate from their proposed DNA binding function. We propose that the Rif1 HEAT repeats region represents a protein-protein binding interface that mediates telomere length regulation.

scholarly journals DNA Binding by the Methanothermobacter thermautotrophicus Cdc6 Protein Is Inhibited by the Minichromosome Maintenance Helicase

2006 ◽  
Vol 188 (12) ◽  
pp. 4577-4580 ◽  
Author(s):  
Rajesh Kasiviswanathan ◽  
Jae-Ho Shin ◽  
Zvi Kelman
Keyword(s):  
Dna Binding ◽  
Binding Activity ◽  
Minichromosome Maintenance ◽  
Single Stranded Dna ◽  
Mutant Proteins ◽  
Dna Binding Activity ◽  
Double Stranded Dna ◽  
Mcm Helicase ◽  
Methanothermobacter Thermautotrophicus

ABSTRACT The Cdc6 proteins from the archaeon Methanothermobacter thermautotrophicus were previously shown to bind double-stranded DNA. It is shown here that the proteins also bind single-stranded DNA. Using minichromosome maintenance (MCM) helicase mutant proteins unable to bind DNA, it was found that the interaction of MCM with Cdc6 inhibits the DNA binding activity of Cdc6.

scholarly journals Drosophila Minichromosome Maintenance 6 Is Required for Chorion Gene Amplification and Genomic Replication

2002 ◽  
Vol 13 (2) ◽  
pp. 607-620 ◽  
Author(s):  
Gina Schwed ◽  
Noah May ◽  
Yana Pechersky ◽  
Brian R. Calvi
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Genetic Dissection ◽  
Minichromosome Maintenance ◽  
Multiple Origins ◽  
Origin Licensing ◽  
Mcm Complex ◽  
Mcm Proteins ◽  
Prereplicative Complex ◽  
Cycle Regulation

Duplication of the eukaryotic genome initiates from multiple origins of DNA replication whose activity is coordinated with the cell cycle. We have been studying the origins of DNA replication that control amplification of eggshell (chorion) genes duringDrosophila oogenesis. Mutation of genes required for amplification results in a thin eggshell phenotype, allowing a genetic dissection of origin regulation. Herein, we show that one mutation corresponds to a subunit of the minichromosome maintenance (MCM) complex of proteins, MCM6. The binding of the MCM complex to origins in G1 as part of a prereplicative complex is critical for the cell cycle regulation of origin licensing. We find that MCM6 associates with other MCM subunits during amplification. These results suggest that chorion origins are bound by an amplification complex that contains MCM proteins and therefore resembles the prereplicative complex. Lethal alleles of MCM6 reveal it is essential for mitotic cycles and endocycles, and suggest that its function is mediated by ATP. We discuss the implications of these findings for the role of MCMs in the coordination of DNA replication during the cell cycle.

scholarly journals Structural Changes in Mcm5 Protein Bypass Cdc7-Dbf4 Function and Reduce Replication Origin Efficiency in Saccharomyces cerevisiae

2007 ◽  
Vol 27 (21) ◽  
pp. 7594-7602 ◽  
Author(s):  
Margaret L. Hoang ◽  
Ronald P. Leon ◽  
Luis Pessoa-Brandao ◽  
Sonia Hunt ◽  
M. K. Raghuraman ◽  
...  
Keyword(s):  
Structural Changes ◽  
S Phase ◽  
Minichromosome Maintenance ◽  
Chromosomal Replication ◽  
Origin Firing ◽  
Highly Active ◽  
Mcm Complex ◽  
Alternate States ◽  
Firing Efficiency ◽  
Intrinsic Firing

ABSTRACT Eukaryotic chromosomal replication is a complicated process with many origins firing at different efficiencies and times during S phase. Prereplication complexes are assembled on all origins in G1 phase, and yet only a subset of complexes is activated during S phase by DDK (for Dbf4-dependent kinase) (Cdc7-Dbf4). The yeast mcm5-bob1 (P83L) mutation bypasses DDK but results in reduced intrinsic firing efficiency at 11 endogenous origins and at origins located on minichromosomes. Origin efficiency may result from Mcm5 protein assuming an altered conformation, as predicted from the atomic structure of an archaeal MCM (for minichromosome maintenance) homologue. Similarly, an intragenic mutation in a residue predicted to interact with P83L suppresses the mcm5-bob1 bypass phenotype. We propose DDK phosphorylation of the MCM complex normally results in a single, highly active conformation of Mcm5, whereas the mcm5-bob1 mutation produces a number of conformations, only one of which is permissive for origin activation. Random adoption of these alternate states by the mcm5-bob1 protein can explain both how origin firing occurs independently of DDK and why origin efficiency is reduced. Because similar mutations in mcm2 and mcm4 cannot bypass DDK, Mcm5 protein may be a unique Mcm protein that is the final target of DDK regulation.

scholarly journals Ring-Shaped Replicative Helicase Encircles Double-Stranded DNA during Unwinding

2020 ◽  
Vol 118 (3) ◽  
pp. 375a
Author(s):  
Mina Lee ◽  
Sihwa Joo ◽  
Tai Hwan Ha
Keyword(s):  
Replicative Helicase ◽  
Double Stranded Dna

scholarly journals Phylogeny of the Serpin Superfamily: Implications of Patterns of Amino Acid Conservation for Structure and Function

2000 ◽  
Vol 10 (12) ◽  
pp. 1845-1864
Author(s):  
James A. Irving ◽  
Robert N. Pike ◽  
Arthur M. Lesk ◽  
James C. Whisstock
Keyword(s):  
Sequence Data ◽  
Initial Point ◽  
Structure And Function ◽  
Conserved Residues ◽  
Consensus Analysis ◽  
The Family ◽  
Protein Sequence Data ◽  
And Function ◽  
Conserved Amino Acids ◽  
Genome Projects

We present a comprehensive alignment and phylogenetic analysis of the serpins, a superfamily of proteins with known members in higher animals, nematodes, insects, plants, and viruses. We analyze, compare, and classify 219 proteins representative of eight major and eight minor subfamilies, using a novel technique of consensus analysis. Patterns of sequence conservation characterize the family as a whole, with a clear relationship to the mechanism of function. Variations of these patterns within phylogenetically distinct groups can be correlated with the divergence of structure and function. The goals of this work are to provide a carefully curated alignment of serpin sequences, to describe patterns of conservation and divergence, and to derive a phylogenetic tree expressing the relationships among the members of this family. We extend earlier studies by Huber and Carrell as well as by Marshall, after whose publication the serpin family has grown functionally, taxonomically, and structurally. We used gene and protein sequence data, crystal structures, and chromosomal location where available. The results illuminate structure–function relationships in serpins, suggesting roles for conserved residues in the mechanism of conformational change. The phylogeny provides a rational evolutionary framework to classify serpins and enables identification of conserved amino acids. Patterns of conservation also provide an initial point of comparison for genes identified by the various genome projects. New homologs emerging from sequencing projects can either take their place within the current classification or, if necessary, extend it.

scholarly journals Mouse APOBEC1 cytidine deaminase can induce somatic mutations in chromosomal DNA

BMC Genomics ◽  
2019 ◽  
Vol 20 (1) ◽  
Author(s):  
Vincent Caval ◽  
Wenjuan Jiao ◽  
Noémie Berry ◽  
Pierre Khalfi ◽  
Emmanuelle Pitré ◽  
...  
Keyword(s):  
Somatic Mutations ◽  
Nuclear Dna ◽  
Cytidine Deaminase ◽  
Cloning And Expression ◽  
Chromosomal Dna ◽  
Dna Breaks ◽  
Cytidine Deaminases ◽  
Double Stranded Dna ◽  
Mammalian Genomes ◽  
Characteristic Features

Abstract Background APOBEC1 (A1) enzymes are cytidine deaminases involved in RNA editing. In addition to this activity, a few A1 enzymes have been shown to be active on single stranded DNA. As two human ssDNA cytidine deaminases APOBEC3A (A3A), APOBEC3B (A3B) and related enzymes across the spectrum of placental mammals have been shown to introduce somatic mutations into nuclear DNA of cancer genomes, we explored the mutagenic threat of A1 cytidine deaminases to chromosomal DNA. Results Molecular cloning and expression of various A1 enzymes reveal that the cow, pig, dog, rabbit and mouse A1 have an intracellular ssDNA substrate specificity. However, among all the enzymes studied, mouse A1 appears to be singular, being able to introduce somatic mutations into nuclear DNA with a clear 5’TpC editing context, and to deaminate 5-methylcytidine substituted DNA which are characteristic features of the cancer related mammalian A3A and A3B enzymes. However, mouse A1 activity fails to elicit formation of double stranded DNA breaks, suggesting that mouse A1 possess an attenuated nuclear DNA mutator phenotype reminiscent of human A3B. Conclusions At an experimental level mouse APOBEC1 is remarkable among 12 mammalian A1 enzymes in that it represents a source of somatic mutations in mouse genome, potentially fueling oncogenesis. While the order Rodentia is bereft of A3A and A3B like enzymes it seems that APOBEC1 may well substitute for it, albeit remaining much less active. This modifies the paradigm that APOBEC3 and AID enzymes are the sole endogenous mutator enzymes giving rise to off-target editing of mammalian genomes.

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