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origin recognition complex subunit 4 OKDB#: 5097
 Symbols: ORC4 Species: human
 Synonyms: ORC4L, ORC4P  Locus: 2q23.1 in Homo sapiens


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General Comment NCBI Summary: The origin recognition complex (ORC) is a highly conserved six subunit protein complex essential for the initiation of the DNA replication in eukaryotic cells. Studies in yeast demonstrated that ORC binds specifically to origins of replication and serves as a platform for the assembly of additional initiation factors such as Cdc6 and Mcm proteins. This gene encodes a subunit of the ORC complex. Several alternatively spliced transcript variants, some of which encode the same protein, have been reported for this gene. [provided by RefSeq, Oct 2010]
General function DNA Replication
Comment
Cellular localization Nuclear
Comment
Ovarian function Oocyte maturation , First polar body extrusion
Comment Higher Order Oligomerization of the Licensing ORC4 Protein Is Required for Polar Body Extrusion in Murine Meiosis. Nguyen H et al. (2017) We have previously shown that the DNA replication licensing factor ORC4 forms a cage around the chromosomes that are extruded in both polar bodies during murine oogenesis, but not around the chromosomes that are retained in the oocyte or around the sperm chromatin. We termed this structure the ORC4 cage. Here, we tested whether the formation of the ORC4 cage is necessary for polar body extrusion (PBE). We first experimentally forced oocytes to extrude sperm chromatin as a pseudo-polar body and found that under these conditions the sperm chromatin did become enclosed in an ORC4 cage. Next, we attempted to prevent the formation of the ORC4 cage by injecting peptides that contained sequences of different domains of the ORC4 protein into metaphase II oocytes just before the cage normally forms. Our rationale was that the ORC4 peptides would block protein-protein interactions required for cage formation. Two out of six tested peptides prevented the ORC4 cage formation and simultaneously inhibited polar body extrusion (PBE), resulting in the formation of two pronuclei that were retained in the oocyte. Together, these data demonstrate that ORC4 oligomerization is required to form the ORC4 cage and that it is required for PBE. This article is protected by copyright. All rights reserved.////////////////// ORC4 Surrounds Extruded Chromatin in Female Meiosis. Nguyen H et al. (2014) Six proteins, ORC1-6, make up the origin recognition complex (ORC) that initiates licensing of DNA replication origins. We have previously reported that subunit ORC2 is localized between the separating maternal chromosomes at anaphase II just after fertilization and is present in zygotic pronuclei at G1. Here, we found that ORC1, 3, and 5 all localize between the chromosomes at anaphase II, but could not be detected in zygotic G1. ORC6 localized to the periphery of the nucleoli at all zygotic stages. We identified an unexpected potential role for ORC4 in polar body formation. We found that in both female meiotic divisions, ORC4 surrounds the set of chromosomes, as a sphere-like structure, that will eventually be discarded in the polar bodies, but not the chromosomes that segregate into the oocyte. None of the other five ORC proteins are involved in this structure. In Zygotic G1, ORC4 surrounds the nuclei of the polar bodies, but was not detectable in the pronuclei. When the zygote entered mitosis ORC4 was only detected in the polar body. However, ORC4 appeared on both sets of separating chromosomes at telophase. At this point, the ORC4 that was in the polar body also migrated into the nuclei, suggesting that ORC4 or an associated protein is modified during the first embryonic cell cycle to allow it to bind DNA. Our results suggest that ORC4 may help identify the chromosomes that are destined to be expelled in the polar body, and may play a role in polar body extrusion. This article is protected by copyright. All rights reserved.//////////////////
Expression regulated by
Comment
Ovarian localization Oocyte
Comment
Follicle stages Preovulatory
Comment
Phenotypes
Mutations 0 mutations
Genomic Region show genomic region
Phenotypes and GWAS show phenotypes and GWAS
Links
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created: Jan. 22, 2015, 10:52 a.m. by: system   email:
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last update: March 1, 2017, 11:40 a.m. by: hsueh    email:



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