Potential calcium sensor that binds calcium in vitro (PubMed:14688294). Modulates homologous recombination and nucleotide excision repair (NER) (PubMed:15155891). Involved in the early response to UV irradiation (PubMed:16786311). Interacts with RAD4 (PubMed:16786311). Calcium is required for this interaction (PubMed:16786311). Interacts with SAC3B (PubMed:19843313). Localizes to the nucleus after exposure to UV-C and cicplatin. A number of isoforms are produced. According to EST sequences. Expressed in leaves, roots, and at lower level in stems. Barely detectable in flower buds and flowers. Up-regulated by UV-C induced DNA damage, but not by DNA double-strand breaks caused by bleomycin. The C-terminal EF-hand is necessary for the binding to RAD4 and for efficient nucleotide excision repair (NER). Belongs to the centrin family. Although assigned as a calmodulin family member by Ref.7, it only contains EF-hand domains.