Human FEM1B is required for Rad9 recruitment and CHK1 activation in response to replication stress

Abstract

Human checkpoint kinase 1 (CHK1) is an essential kinase required to preserve genome stability, and is activated by DNA replication blockage through the ataxia-telangiectasia-mutated-and-Rad3-related (ATR)/ATRIP-signaling pathway. In this report, we show that a novel CHK1-interacting protein, FEM1B (human homologue of the Caenorhabditis elegans sex determination fem1 protein), identified by a yeast two-hybrid screen, is involved in the activation of CHK1 by replication stress. Depletion of FEM1B by small interfering RNA in cancer cells impairs the activation of CHK1 kinase activity and attenuates the induction of CHK1 Ser345 phosphorylation upon replication interference. It is to be noted that, CHK2 Thr68 phosphorylation is not altered by FEM1B downregulation. By fractionation, we further demonstrated that FEM1B is able to associate with chromatin, and such association facilitates chromatin loading of the Rad9 protein. Consistently, ATR activity is poorly maintained in FEM1B knockdown cells; and FEM1B-ablated cells are as sensitive to replication block as CHK1-depleted cells. Our study has uncovered an adaptor protein FEM1B, which acts as a bridge linking CHK1 and Rad9, thus facilitating checkpoint signaling induced by replication stress.

The EHEC-host interactome reveals novel targets for the translocated intimin receptor

“…As for EHEC EspO1-1 we discovered another interaction with fem-1 homolog b (Fem1b), a component of an E3 ubiquitin-protein ligase complex acting as substrate recognition subunit 50 . Fem1b interacts with the checkpoint kinase CHEK1 to sense replication stress 51 and can act as a proapoptotic protein in cancer cells 52 53 54 . EHEC EspO1-1 may be another candidate that could act anti-apoptotically through its Fem1b interaction.…”

Leveraging selective hippocampal vulnerability among Alzheimer’s disease subtypes reveals a novel tau binding partner SERPINA5

“…SLC38A2 functions as a sodium-dependent amino acid transporter that mediates both the efflux of neutral α-amino acids across the blood-brain barrier and their uptake into neurons [67][68][69] . FEM1B is an ankyrin repeat protein that induces replication stress signaling through its interaction with checkpoint kinase 1 70 , regulates ubiquitin-protein transferase activity 71 and promotes apoptosis 72 . PYDC1 (also known as ASC2/POP1) regulates the innate immune response by suppressing NFκB transcription factor activity and pro-caspase-1 activation 73 .…”

A recurrent missense variant in the E3 ubiquitin ligase substrate recognition subunit FEM1B causes a rare syndromic neurodevelopmental disorder

“…Similarly, FEM1B (Fem1 homolog B, MIM 613539) is a CRL2 substrate recognition subunit with a VHL-box for assembly with the other components of the E3 complex: Elongin C ( ELOC , MIM 600788) and Cullin 2 ( CUL2 , MIM 603135) 4 . FEM1B is a ubiquitous protein, localizing mainly in the cytoplasm, but studies based on cellular fractionation have also suggested a role in the nucleus 5 .…”

“…Several functions of FEM1B include roles in apoptosis 6 , 7 , glucose homeostasis 8 , secondary sexual development 9 , replication stress pathways 5 , and more recently reductive stress pathways 10 , 11 . Although few FEM1B-substrate interactions have been resolved at the molecular level, FEM1B has been shown to interact with distinct types of amino-acid sequences, termed degrons.…”