The DDB1a interacting proteins ATCSA-1 and DDB2 are critical factors for UV-B tolerance and genomic integrity in Arabidopsis thaliana

Abstract

Summary The integrity of the genome is a fundamental prerequisite for the well‐being of all living organisms. Critical for the genomic integrity are effective DNA damage detection mechanisms that enable the cell to rapidly activate the necessary repair machinery. Here, we describe Arabidopsis thaliana ATCSA‐1, which is an ortholog of the mammalian Cockayne Syndrome type‐A protein involved in transcription‐coupled DNA repair processes. ATCSA‐1 is a critical component for initiating the repair of UV‐B‐induced DNA lesions, and, together with the damage‐specific DNA binding protein 2 (DDB2), is necessary for light‐independent repair processes in Arabidopsis. The transcriptional profile of both genes revealed that ATCSA‐1 is strongly expressed in most tissues, whereas DDB2 is only weakly expressed, predominantly in the root tips and anthers of flowers. In contrast to ATCSA‐1, DDB2 expression is rapidly inducible by UV treatment. Like DDB2, ATCSA‐1 is localized to the nucleus, and assembles with DDB1 and CUL4 proteins into a complex. ATCSA‐1 is an unstable protein that is degraded in a 26S proteasome‐dependent manner. Overall, the results presented here form a functional description of a plant Cockayne syndrome factor A (CSA) ortholog, and demonstrate the importance of ATCSA‐1 for UV‐B tolerance.

Regulation of Abiotic Stress Signal Transduction by E3 Ubiquitin Ligases in Arabidopsis

“…Recently, two DWD genes, an ortholog of the mammalian Cockayne Syndrome type-A (AtCSA-1) and damage-specific DNA binding protein 2 (DDB2), were reported as crucial components in UV-B response (Biedermann and Hellmann, 2010;Zhang et al, 2010). As AtCSA-1 and DDB2 form CRL4 complexes with DDB1 and CUL4, it is possible that CRL4 E3 ligase acts as an important regulator in UV-B response (Biedermann and Hellmann, 2010;Zhang et al, 2010).…”

“…As AtCSA-1 and DDB2 form CRL4 complexes with DDB1 and CUL4, it is possible that CRL4 E3 ligase acts as an important regulator in UV-B response (Biedermann and Hellmann, 2010;Zhang et al, 2010).…”

UV Damaged DNA Repair & Tolerance in Plants

“…This result is hypothesised to be due to competition between CSA and with other DWD proteins to interact with the DDB1-CUL4 complex. Interestingly AtCSA1A levels remained constant upon UV induction (Biedermann & Hellmann, 2010). RNAi of a putative Arabidopsis CSB homolog resulted in a UV sensitive phenotype (Shaked et al, 2006).…”

“…AtDDB2 encodes a 48 kDa nuclear localized protein with upregulated expression upon UV-induction. AtDDB2 loss of function results in UV sensitivity while overexpression increases UV tolerance (Biedermann & Hellmann, 2010;Koga et al, 2006;Molinier et al, 2008).…”

“…AtCUL4 loss of function results in abnormal plant development (Bernhardt et al, 2006;Chen et al, 2006) and UV sensitivity (Molinier et al, 2008). Examples of DCAF proteins interacting with the Arabidopsis CUL4-DDB1A/B complex include AtDDB2 (Bernhardt et al, 2006), AtCSA-1&2 (Biedermann & Hellmann, 2010;Zhang et al, 2010), as well as the negative regulator of photomorphogenesis DET1 (De-etiolated1) (Schroeder et al, 2002), and many other DWD proteins . Recent results have shed light on the cross talk between photomorphogenesis regulation and repair of UV damaged DNA.…”