CpG islands (CGIs) are key regulatory DNA elements at most promoters, but how they influence the chromatin status and transcription remains elusive. Here, we identify and characterize SAMD1 (SAM domain-containing protein 1) as an unmethylated CGI-binding protein. SAMD1 has an atypical winged-helix domain that directly recognizes unmethylated CpG-containing DNA via simultaneous interactions with both the major and the minor groove. The SAM domain interacts with L3MBTL3, but it can also homopolymerize into a closed pentameric ring. At a genome-wide level, SAMD1 localizes to H3K4me3-decorated CGIs, where it acts as a repressor. SAMD1 tethers L3MBTL3 to chromatin and interacts with the KDM1A histone demethylase complex to modulate H3K4me2 and H3K4me3 levels at CGIs, thereby providing a mechanism for SAMD1-mediated transcriptional repression. The absence of SAMD1 impairs ES cell differentiation processes, leading to misregulation of key biological pathways. Together, our work establishes SAMD1 as a newly identified chromatin regulator acting at unmethylated CGIs.

Background: Sp4 is a zinc finger transcription factor which is closely related to Sp1 and Sp3. All three proteins recognize the same DNA elements and can act as transcriptional activators through glutaminerich activation domains. Unlike Sp1 and Sp3, which are ubiquitous proteins, Sp4 is highly abundant in the central nervous system, but also detectable in many other tissues.

BACKGROUND Protein S is a plasma protein that serves as an important cofactor for activated protein C in the blood anticoagulation system. Protein S also acts as a mitogen on distinct cell types and is a ligand for Tyro3, a member of the Axl family of oncogenic receptor tyrosine kinases. This lends support to the hypothesis that protein S might also be involved in tumor cell regulation. METHODS The expression of protein S and receptor Tyro3 was examined in 22 lung carcinoma cell lines and normal bronchial epithelial cells by reverse transcriptase–polymerase chain reaction. Secreted protein S was identified by Western blot analysis of cell supernatants and tested in a protein S–dependent clotting test for anticoagulant activity. Immunohistochemistry with anti–protein S polyvalent antiserum was also performed on 31 primary lung carcinoma specimens. RESULTS Protein S mRNA and secreted protein were found in 11 of 12 cell lines of nonsmall cell lung carcinoma (NSCLC) origin and in normal bronchial epithelial cells, but they were found in only 4 of 10 small cell lung carcinoma (SCLC) cell lines. The majority of lung carcinoma cell lines that expressed protein S (13 of 15) also revealed expression of the cognate receptor, Tyro3. Protein S that was present in cell supernatant had anticoagulant activity comparable to that of plasma protein S, suggesting that it is γ‐carboxylated. In lung tumor tissue, protein S antigen was found in 20 of 31 cases examined, predominantly in tumors of the squamous cell and bronchioalveolar cell types. Protein S was found not only in tumor cells but also in cells of the normal bronchial epithelium, in alveolar macrophages, and in endothelium. CONCLUSIONS To the authors' knowledge, their report is the first of the synthesis of an active anticoagulant protein in epithelial cells of human cancer. It suggests that protein S, by binding to a receptor (Tyro3), may influence local anticoagulation events or other, as yet unidentified, aspects of lung tumor development. Cancer 1999;86:43–9. © 1999 American Cancer Society.

The lysine acetyltransferase KAT6A (MOZ, MYST3) belongs to the MYST family of chromatin regulators, facilitating histone acetylation. Dysregulation of KAT6A has been implicated in developmental syndromes and the onset of acute myeloid leukemia (AML). Previous work suggests that KAT6A is recruited to its genomic targets by a combinatorial function of histone binding PHD fingers, transcription factors and chromatin binding interaction partners. Here, we demonstrate that a winged helix (WH) domain at the very N-terminus of KAT6A specifically interacts with unmethylated CpG motifs. This DNA binding function leads to the association of KAT6A with unmethylated CpG islands (CGIs) genome-wide. Mutation of the essential amino acids for DNA binding completely abrogates the enrichment of KAT6A at CGIs. In contrast, deletion of a second WH domain or the histone tail binding PHD fingers only subtly influences the binding of KAT6A to CGIs. Overexpression of a KAT6A WH1 mutant has a dominant negative effect on H3K9 histone acetylation, which is comparable to the effects upon overexpression of a KAT6A HAT domain mutant. Taken together, our work revealed a previously unrecognized chromatin recruitment mechanism of KAT6A, offering a new perspective on the role of KAT6A in gene regulation and human diseases.