Arabidopsis Cockayne Syndrome A-Like Proteins 1A and 1B Form a Complex with CULLIN4 and Damage DNA Binding Protein 1A and Regulate the Response to UV Irradiation

Abstract

In plants, as in animals, DNA is constantly subject to chemical modification. UV-B irradiation is a major genotoxic agent and has significant effects on plant growth and development. Through forward genetic screening, we identified a UV-Bsensitive mutant (csaat1a-3) in Arabidopsis thaliana, in which expression of CSAat1A, encoding a Cockayne Syndrome A-like protein, is reduced due to insertion of a T-DNA in the promoter region. Arabidopsis lacking CSAat1A or its homolog CSAat1B is more sensitive to UV-B and the genotoxic drug methyl methanesulfonate and exhibits reduced transcriptioncoupled repair activity. Yeast two-hybrid analysis indicated that both CSAat1A and B interact with DDB1A (UV-Damage DNA Binding Protein1). Coimmunoprecipitation assays demonstrated that CSAat1A and B associate with the CULLIN4 (CUL4)-DDB1A complex in Arabidopsis. A split-yellow fluorescent protein assay showed that this interaction occurs in the nucleus, consistent with the idea that the CUL4-DDB1A-CSA complex functions as a nuclear E3 ubiquitin ligase. CSAat1A and B formed heterotetramers in Arabidopsis. Taken together, our data suggest that the plant CUL4-DDB1A CSAat1A and B complex represents a unique mechanism to promote ubiquitination of substrates in response to DNA damage.

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).…”

The tomato DWD motif-containing protein DDI1 interacts with the CUL4–DDB1-based ubiquitin ligase and plays a pivotal role in abiotic stress responses

“…Genetic impairing of CUL4, DDB1, or DDB2 leads to similar hypersensitivity to UV-C [23]. Further research revealed that, in addition to DDB2, another DWD-containing protein CSA1 (Cockayne syndrome factor A) is also involved in repairing UV-damaged DNA in conjunction with CUL4 [24]. We found significantly altered responses to UV-radiation in transgenic tomato lines with overexpression or knockdown of DDI1 gene, A schematic diagram for the UV-C treatment assay.…”

UV Damaged DNA Repair & Tolerance in Plants

“…These proteins exist as heterotetramers in planta and are capable of interacting with the DDB1-CUL4 E3 complex. Knockouts of either gene result in UV sensitivity and decreased photoproduct removal (Zhang et al, 2010). Concurrently, another group overexpressed AtCSA1A, which surprisingly also resulted in increased UV sensitivity.…”

“…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.…”