, 2008). Therefore, to characterize the histone acetylation activity of LdHAT1, in vitro assays were carried out using a peptide substrate derived from the N-terminus of L. donovani histone H4. To identify the lysine residue that was specifically acetylated Trametinib ic50 by LdHAT1, three antibodies were raised against L. donovani histone H4–derived peptides acetylated on K4, K10 or K14 residue, respectively. Specificities of the antibodies were ensured by dot blot analysis, which showed no cross-reactivity (Fig. 3a).

Once the specificities were confirmed, the antibodies were used to identify the lysine residue on the peptide derived from N-terminus of L. donovani histone H4 acetylated by LdHAT1. As shown in Fig. 3b, the peptide acetylated by LdHAT1 could be detected only by anti-H4K10Ac antibody, but not with other two antibodies (data not shown), suggesting that the acetyltransferase from L. donovani specifically acetylates H4K10 residue. As LdHAT1 was shown to be phosphorylated by S-phase kinase LdCyc1-CRK3, it would be interesting to investigate

any possible effect of such phosphorylation on its histone acetylation activity. To explore such a possibility, H4K10 acetylation activity of non-phosphorylated LdHAT1 was compared with that of LdHAT1 phosphorylated by LdCyc1-CRK3. As depicted in Fig. 3c, the phosphorylated form of LdHAT1 did not show SB203580 concentration any H4K10 acetylation activity, suggesting the regulation of histone H4 acetylation by S-phase cell cycle kinase. Intriguingly, LdHAT1ΔCy and LdHAT1-T394A mutants also did not show any acetylation activity (Fig. 3d) implicating the contribution of the mutated residues in the enzymatic activity. Previous studies demonstrated the acetylation ID-8 of K4, K10 and K14 residues of the N-terminal tail of histone H4 from T. brucei and T. cruzi (da

Cunha et al., 2006; Janzen et al., 2006; Mandava et al., 2007). Moreover, cell cycle-dependent post-S-phase enhancement of K4, K10 and K14 acetylation of histone H4 was observed in T. cruzi (Nardelli et al., 2009). Therefore, the observed inhibition of histone H4K10 acetylation by LdHAT1 owing to its phosphorylation by S-phase kinase in the present studies could correlate such cell cycle–specific periodic acetylation. It will be interesting to study the effect of inhibition of the HAT activity on the S-phase events. The work was partially supported by the project grant [37(1044)/00/EMR-II] from Council of Scientific and Industrial Research (CSIR), India and intramural grant from Department of Atomic Energy, Government of India. The authors have no conflict of interest to declare. “
“Metagenomic DNA libraries constructed from the Dagong Ancient Brine Well were screened for genes with Na+/H+ antiporter activity on the antiporter-deficient Escherichia coli KNabc strain. One clone with a stable Na+-resistant phenotype was obtained and its Na+/H+ antiporter gene was sequenced and designated as m-nha.