Protein Kinase CK2 Phosphorylates the High Mobility Group Domain Protein SSRP1, Inducing the Recognition of UV-damaged DNA

• Published in: The Journal of biological chemistry Vol. 278; no. 15; pp. 12710 - 12715
• Main Authors: Krohn, Nicholas M, Stemmer, Christian, Fojan, Peter, Grimm, Rudi, Grasser, Klaus D
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 11.04.2003
• Subjects: Amino Acid Substitution; Base Sequence; Casein Kinase II; Circular Dichroism; DNA - metabolism; DNA - radiation effects; DNA Damage; DNA Primers; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; High Mobility Group Proteins - chemistry; High Mobility Group Proteins - genetics; High Mobility Group Proteins - metabolism; Humans; Kinetics; Phosphorylation; Plant Proteins - genetics; Plant Proteins - metabolism; Protein Conformation; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - metabolism; Recombinant Proteins - metabolism; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Transcriptional Elongation Factors; Ultraviolet Rays; Zea mays - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M300250200

The structure-specific recognition protein SSRP1 plays a role in transcription and replication in the chromatin context. Mediated by its C-terminal high mobility group (HMG) box domain, SSRP1 binds DNA non-sequence specifically but recognizes certain DNA structures. Using acetic acid urea polyacrylamide gel electrophoresis and mass spectrometry, we have examined the phosphorylation of maize SSRP1 by protein kinase CK2α. The kinase phosphorylated several amino acid residues in the C-terminal part of the SSRP1 protein. Two phosphorylation sites were mapped in the very C-terminal region next to the HMG box domain, and about seven sites are localized within the acidic domain. Circular dichroism showed that the phosphorylation of the two C-terminal sites by CK2α resulted in a structural change in the region of HMG box domain, because the negative peak of the CD spectrum at 222 nm was decreased by ∼10%. In parallel, the phosphorylation induced the recognition of UV-damaged DNA, whereas the non-phosphorylated protein does not discriminate between UV-damaged DNA and control DNA. The affinity of CK2α-phosphorylated SSRP1 for the DNA correlates with the degree of UV-induced DNA damage. Moreover, maize SSRP1 can restore the increased UV-sensitivity of a yeast strain lacking the NHP6A/B HMG domain proteins to levels of the control strain. Collectively, these findings indicate a role for SSRP1 in the UV response of eukaryotic cells.