ATM Substrate Chk2-interacting Zn2+ Finger (ASCIZ) Is a Bi-functional Transcriptional Activator and Feedback Sensor in the Regulation of Dynein Light Chain (DYNLL1) Expression

Abstract

Background:The regulation of multi-functional DYNLL1 is poorly understood. Results: ASCIZ activates Dynll1 gene expression and is inhibited by DYNLL1 binding to its transcription activation domain. Conclusion: ASCIZ plays a key role in the auto-regulation of DYNLL1 levels. Significance: This is the first case where a gene product directly inhibits its main transcriptional activator while bound at its own promoter.

ATMIN (ATM Interactor)

“…ASCIZ protein sequences are highly conserved amongst all vertebrates from fish to mammals (Kanu and Behrens, 2007;Jurado et al, 2012a). The ASCIZ protein is structurally and functionally conserved in Drosophila, where it also contains four N-terminal Zinc-fingers and a TQT-rich C-terminal transcription activation domain, condensed into only 388 amino acid residues (Zaytseva et al, 2014).…”

“…Loss of ASCIZ leads to increased cell death in response to methylating or oxidating DNA damage in human, mouse and chicken cells (McNees et al, 2005;Oka et al, 2008;Jurado et al, 2010;Kanu et al, 2010), and increased basal IgV gene conversion rates in the chicken DT40 B cell line (Oka et al, 2008). ASCIZ focus formation in response to methylating agents depends on DYNLL1 (Jurado et al, 2012a), but it is not known whether this also involves its transcription factor function. The B cell developmental defect of conditional Asciz/Atmin KO mice could not be rescued by deletion of tp53 or complementation with a pre-arranged B cell receptor transgene (Jurado et al, 2012b), supporting a DNA damageindependent mechanism as cause of the B cell deficiency.…”

“…Conditional Asciz/Atmin KO mice generated using B lympoid-specific Cd19-Cre (Loizou et al, 2011) or Mb1-Cre (Jurado et al, 2012b) have reduced peripheral B cell numbers due to increased apoptotic cell death during B cell development in the bone marrow. The most highly downregulated gene in Ascizdeficient cells is the dynein light chain subunit Dynll1 (Jurado et al, 2012a). Strikingly, DYNLL1 protein can in turn bind to about a dozen individual sites -mostly encompassing TQT motifs -in the ASCIZ transcription activation domain (Rapali et al, 2011;Jurado et al, 2012a) and thereby inhibit its transcriptional activity in a concentrationdependent manner (Jurado et al, 2012a), which provides a feedback mechanism to maintain stable DYNLL1 protein levels.…”

“…The most highly downregulated gene in Ascizdeficient cells is the dynein light chain subunit Dynll1 (Jurado et al, 2012a). Strikingly, DYNLL1 protein can in turn bind to about a dozen individual sites -mostly encompassing TQT motifs -in the ASCIZ transcription activation domain (Rapali et al, 2011;Jurado et al, 2012a) and thereby inhibit its transcriptional activity in a concentrationdependent manner (Jurado et al, 2012a), which provides a feedback mechanism to maintain stable DYNLL1 protein levels. The ability of ASCIZ to regulate expression of and bind to the DYNLL1-like dynein light chain (called Cutup) is conserved in Drosophila (Zaytseva et al, 2014).…”

“…Human ASCIZ contains 20 potential ATM/ATR kinase phosphorylation sites, most of which are clustered in an SQ/TQ cluster domain coinciding with the transcription activation domain (Heierhorst et al, 2011). 11 of these sites are TQT motifs and represent binding sites for the DYNLL1 protein (Rapali et al, 2011;Jurado et al, 2012a).…”