Entry

Hou and Zou (2005) found that the C-terminal half of EFO2 possessed autoacetylation activity. RNA interference in HeLa cells showed that EFO2 was required for sister chromatid cohesion. There was a significant increase in mitotic cells with unpaired chromatids (65%) when EFO2 was depleted and a further increase in unpaired chromatids (93%) when both EFO1 and EFO2 were reduced simultaneously. Depletion of EFO1 or EFO2 resulted in an enrichment in G2/M cells, an increase in cells with chromosomes scattered along spindles, and an increase in cells with multipole spindles. However, depletion of EFO1 or EFO2 had no effect on the binding of cohesin (see 606462) with chromosomes in interphase cells. All cellular effects were exacerbated in cells depleted of both EFO1 and EFO2. In HeLa and 293T human embryonic kidney cells, about 70% of endogenous EFO1 and EFO2 associated with chromosomes, but the 2 proteins were differentially regulated during the cell cycle. EFO1 remained on chromosomes in mitosis, whereas EFO2 dissociated from chromosomes and/or was degraded. Mutation analysis indicated that binding of EFO1 or EFO2 to chromosomes was mediated by their diverse N termini.

Moldovan et al. (2006) found that yeast Eco1 and human ESCO2 interacted directly with PCNA (176740) via a conserved PIP box variant in their N termini. Yeast Eco1 mutants deficient in Eco1-Pcna interaction were defective in chromatid cohesion and inviable. Moldovan et al. (2006) concluded that PCNA is crucially involved in the establishment of cohesion in S phase.

Using immunoprecipitation analysis, Kim et al. (2008) showed that human ESCO2 interacted with components of the COREST corepressor complex, including COREST (RCOR; 607675). ESCO2 also interacted with various histone methyltransferases, including SUV39H1 (300254), SETDB1 (604396), and G9A (EHMT2; 604599), and the ESCO2 complex displayed histone H3 (see 602810) lys9 (H3K9) methyltransferase activity and transcription repression activity. The COREST complex, SETDB1, and SUV39H1 were required for ESCO2-mediated transcriptional repression. Furthermore, transcriptional repression by ESCO2 correlated with changes in histone tail modification, indicating that ESCO2 repressed transcription through modulation of chromatin structure.

Through single-molecule analysis, Terret et al. (2009) demonstrated that a replication complex, the RFC-CTF18 clamp loader (see 613201), controls the velocity spacing and restart activity of replication forks in human cells and is required for robust acetylation of cohesin's SMC3 subunit (606062) and sister chromatid cohesion. Unexpectedly, Terret et al. (2009) discovered that cohesin acetylation itself is a central determinant of fork processivity, as slow-moving replication forks were found in cells lacking the Eco1-related acetyltransferases ESCO1 or ESCO2 (including those derived from patients with Roberts syndrome (268300), in whom ESCO2 is biallelically mutated), and in cells expressing a form of SMC3 that cannot be acetylated. This defect was a consequence of cohesin's hyperstable interaction with 2 regulatory cofactors, WAPL (610754) and PDS5A (613200); removal of either cofactor allowed forks to progress rapidly without ESCO1, ESCO2, or RFC-CTF18. Terret et al. (2009) concluded that their results showed a novel mechanism for clamp loader-dependent fork progression, mediated by the posttranslational modification and structural remodeling of the cohesin ring. Loss of this regulatory mechanism leads to the spontaneous accrual of DNA damage and may contribute to the abnormalities of the Roberts syndrome cohesinopathy.

By in situ hybridization of human embryos, Vega et al. (2010) found expression of ESCO2 in brain, first and third branchial arches, otocyst, dorsal root ganglia, limb buds, kidney, and gonads. At Carnegie stage (CS) 14 (32 days postovulation), ESCO2 expression was detected in the neuroepithelium of the hindbrain, midbrain, telencephalic vesicle, otocyst, mandibular component of the first and third branchial arches, and developing dorsal root ganglia. At the limb buds, ESCO2 showed a homogeneous mesenchymal expression pattern. There was absence of detectable expression in the eye, surrounding vertebral body and ribs, and cardiac tissues and developing great vessels at the stages tested. At CS 17 (41 days postovulation), expression in the limbs was confined to discrete zones in the developing hand plate. At CS 21 (52 days postovulation), expression appeared confined to areas surrounding the distal tip of the cartilaginous bone of the long bones of the forearm, wrist, and phalanges and underlying the developing sternum. In kidney, expression at CS 21 was localized to the metanephric cortex and male gonadal epithelium.