The phenotype of the minichromosome maintenance mutant mcm3 is characteristic of mutants defective in DNA replication.

Abstract

MCM3 is an essential gene involved in the maintenance of minichromosomes in yeast cells. It encodes a protein of 971 amino acids that shows striking homology to the Mcm2 protein. We have mapped the mcm3-1 mutation on the left arm of chromosome V approximately 3 kb centromere proximal of anpl. The mcm3-1 mutant was found to be thermosensitive for growth. Under permissive growth conditions, it was defective in minichromosome maintenance in an autonomously replicating sequence-specific manner and showed an increase in chromosome loss and recombination. Under nonpermissive conditions, mcm3-1 exhibited a cell cycle arrest phenotype, arresting at the large-bud stage with an undivided nucleus that had a DNA content of nearly 2n. These phenotypes are consistent with incomplete replication of the genome of the mcm3-1 mutant, possibly as a result of limited replication initiation at selective autonomously replicating sequences leading to cell cycle arrest before mitosis. The phenotype exhibited by the mcm3 mutant is very similar to that of mcm2, suggesting that the Mcm2 and Mcm3 proteins may play interacting roles in DNA replication.

Depletion of minichromosome maintenance protein 5 in the zebrafish retina causes cell-cycle defect and apoptosis

“…With the reduced level of functional MCM complex in mcm5 m850 mutants, fewer replication forks would likely be initiated, and the elongation of existing replication forks might slow, perhaps resulting in delayed progression through S phase. Interestingly, many mcm5 m850 mutant cells accumulate near 4C peak and may have finished replicating the bulk of their DNA, reminiscent of the situation in budding yeast mcm mutants, which exhibit a cell-division-cycle arrest in S phase, with a nearly doubled DNA content (41,42).…”

Molecular cloning of cDNA encoding mouse Cdc21 and CDC46 homologs and characterization of the products: physical interaction between P1 (MCM3) and CDC46 proteins

“…2). Most of these proteins were extracted with 0.5 M NaCl as P1MCM3 (15 (24,27 (3,7,15). The blot with the anti-mCDC21 also showed a signal at 75 kDa in the cytoplasmic and the wash fractions.…”

“…All genes examined in yeasts are essential for cell growth and their mutation causes cell cycle arrest in S phase (3,4,(6)(7)(8)(9)(10)16). In mammalian cells, DNA replication is inhibited when antibody against human MCM2 homolog, BM28 (14) or mouse P1MCM3 (15) is microinjected into the nucleus.…”

“…However, little is known about the regulatory mechanism of the co-ordinated initiation of DNA replication for the multiple replication origin. Budding yeast minichromosome maintenance (MCM) proteins have been postulated to be involved in the initiation of DNA replication by acting at the replication origin, since the mutation of these genes showed an autonomously replicating sequence (ARS)-specific minichromosome maintenance defect in addition to phenotypes with increased chromosome loss and recombination (1)(2)(3)(4)(5). Recently, inhibition of the initiation not only at an ARS on a minichromosome but at a specific chromosomal origin of DNA replication was shown in mcm2-1 and mcm3-1 mutants (6).…”

“…The Mcm gene family is conserved from yeast (3,4,(7)(8)(9)(10)(11) to mammals (12)(13)(14)(15) and consists of at least six members (Table 1). All genes examined in yeasts are essential for cell growth and their mutation causes cell cycle arrest in S phase (3,4,(6)(7)(8)(9)(10)16).…”