This phenomenon remains currently unexplained but is in line with previously proposed cell cycle checkpoint functions of this protease, that when absent may sensitize cells to apoptosis.
Collectively, our data show that the checkpoint function of the FHA domain of CHFR is a core component of anti-proliferative properties against the gastrointestinal carcinogenesis.
A previous study has indicated that the ΔFHA mutant of CHFR acts as a dominant-negative and can disrupt the checkpoint function of the wild type protein [1].
Our data further suggest that an off-target effect may similarly explain the purported checkpoint function of the Tao1 kinase.
A mitotic checkpoint function of the Aurora B kinase complex, independently of generating unattached kinetochores, has previously been documented in vertebrates and fission yeast [ 24 27].
By the use of a cell cycle checkpoint assay, we also confirmed that the FHA domain of CHFR plays an important role in initiating a cell cycle arrest at G2/M, indicating a functional link exists between the anti-proliferative effects and checkpoint function of this tumor suppressor protein via this domain.
In other systems, the checkpoint functions of ATR and ATM are mediated by the checkpoint effector kinases Chk1 and Chk2, respectively [17].
Therefore, to assess checkpoint functions of Chk1D469A and Chk1D469G we evaluated the ability of the mutant alleles to support survival upon generation of a variety of other types of DNA damage.
We also examined if the different mec1 alleles interacted with Lcd1/ Ddc2 (ATRIP in mammalian cells), an association required for the checkpoint functions of Mec1 (Rouse and Jackson 2000; Paciotti et al. 2000; Wakayama et al. 2001).
However, it is possible that the pathways identified by our differential gene expression analysis influence the exact checkpoint functions of ARTEMIS, perhaps in a cell type-dependent fashion, and may thus account for the phenotypic differences we observe in ArtΔ/Δ MSCs versus other cell types [ 12- 14].
