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Summary Centromeres, the specialized chromosomal regions for recruiting kinetochores and directing chromosome segregation, are epigenetically marked by a centromeric histone H3 variant, CENP-A. To maintain centromere identity through cell cycles, CENP-A diluted during DNA replication is replenished. The licensing factor M18BP1 KNL-2 is known to recruit CENP-A to holocentromeres. Here, we show that RbAp46/48 LIN-53 , a conserved histone chaperone, is required for CENP-A HCP-3 localization in holocentric Caenorhabditis elegans . Indeed, RbAp46/48 LIN-53 and CENP-A HCP-3 localizations are interdependent. RbAp46/48 LIN-53 localizes to the centromere during metaphase in a CENP-A HCP-3 - and M18BP1 KNL-2 -dependent manner, suggesting CENP-A HCP-3 loading may occur before anaphase. RbAp46/48 LIN-53 does not function at the centromere through histone acetylation, H3K27 trimethylation, or its known chromatin-modifying complexes. RbAp46/48 LIN-53 may function independently to escort CENP-A HCP-3 for holocentromere assembly but is dispensable for other kinetochore protein recruitment. Nonetheless, depletion of RbAp46/48 LIN-53 leads to anaphase bridges and chromosome missegregation. This study unravels the holocentromere assembly hierarchy and its conservation with monocentromeres. [ABSTRACT FROM AUTHOR]

Abstract: Toll/Toll-like receptors (TLRs), one of the most important pattern recognition receptors (PRRs), play a crucial role in innate immune responses in both invertebrates and vertebrates. In this study, we cloned and characterised a Toll gene from Scylla paramamosain (SpToll). Bioinformatic analysis predicted that SpToll contained one open reading frame of 3018bp and encoded a single-pass transmembrane domain protein of 1005 amino acids. Further, SpToll could be clustered into one branch along with other arthropod Tolls in a phylogenetic tree. SpToll transcripts could be detected by RT-PCR from all tissues examined including the heart, gill, hepatopancreas, stomach, intestine, muscle, eyestalk and hemocytes. Infection by Vibrio parahemolyticus up-regulated SpToll mRNA expression in hemocytes after 48h. The profile of single nucleotide polymorphisms (SNPs) in the leucine-rich repeats (LRRs) domain of SpToll in three healthy crabs was then evaluated. Two hundred and twenty SNPs with a frequency of about 1.0–4.0% were identified in hemocyte DNA/cDNA. Surprisingly, the adenine to guanine transition at position 1372 (c.1372A>G) had a frequency of about 50%. Finally, the results showed that challenge with V. parahemolyticus stimulated the appearance of two sets of SNPs in crabs. More importantly, the c.1372A>G mutation could contribute to a low mortality after V. parahemolyticus infection and introduce variation of charge and secondary structure into the SpToll polypeptide. In summary, these studies suggested a novel Toll homologue in crab and identified a SNP with potential pathogen-resistant activities. The result will be important for the investigation of crab immune defense mechanisms. [Copyright &y& Elsevier]

Hemocyanin, a copper-containing respiratory protein, is abundantly present in hemolymph of arthropods and mollusks and performs a variety of immunological functions. However, the regulatory mechanisms of hemocyanin gene transcription remain largely unclear. Our previous work showed that knockdown of the transcription factor CSL, a component of the Notch signaling pathway, downregulated the expression of Penaeus vannamei hemocyanin small subunit gene (Pv HMCs), indicating the involvement of CSL in regulating the Pv HMCs transcription. In this study, we identified a CSL binding motif ("GAATCCCAGA", +1675/+1684 bp) in the core promoter of Pv HMCs (designated as HsP3). Dual luciferase reporter assay and electrophoretic mobility shift assay (EMSA) demonstrated that the CSL homolog in P. vannamei (Pv CSL) could directly bind and activate the HsP3 promoter. Moreover, in vivo silencing of Pv CSL significantly attenuated the mRNA and protein expression of Pv HMCs. Finally, in response to Vibrio parahaemolyticus , Streptococcus iniae and white spot syndrome virus (WSSV) challenge, the transcript of Pv CSL and Pv HMCs showed a positive correlation, suggesting that Pv CSL could also modulate the expression of Pv HMCs upon pathogen stimulation. Taken together, our present finding is the first to demonstrate that Pv CSL is a crucial factor in transcriptional control of Pv HMCs. • A CSL binding motif was identified in the core promoter of Penaeus vannamei hemocyanin small subunit gene (Pv HMCs). • P. vannamei CSL (Pv CSL) functioned as a transcriptional activator of Pv HMCs. • Transcript of Pv CSL and Pv HMCs was positively correlated upon pathogen infection. [ABSTRACT FROM AUTHOR]