Structural basis of HP1/PXVXL motif peptide interactions and HP1 localisation to heterochromatin

HP1 family proteins are adaptor molecules, containing two related chromo domains that are required for chromatin packaging and gene silencing. Here we present the structure of the chromo shadow domain from mouse HP1beta bound to a peptide containing a consensus PXVXL motif found in many HP1 binding partners. The shadow domain exhibits a novel mode of peptide recognition, where the peptide binds across the dimer interface, sandwiched in a beta-sheet between strands from each monomer. The structure allows us to predict which other shadow domains bind similar PXVXL motif-containing peptides and provides a framework for predicting the sequence specificity of the others. We show that targeting of HP1beta to heterochromatin requires shadow domain interactions with PXVXL-containing proteins in addition to chromo domain recognition of Lys-9-methylated histone H3. Interestingly, it also appears to require the simultaneous recognition of two Lys-9-methylated histone H3 molecules. This finding implies a further complexity to the histone code for regulation of chromatin structure and suggests how binding of HP1 family proteins may lead to its condensation.     

Length-weight relationship of seven bycatch fish species caught along the Chennai coast,Bay of Bengal,Eastern Indian Ocean

Length-weight relationships (LWRs) were estimated for seven fish species captured as bycatch along the Chennai coast, Bay of Bengal, Eastern Indian Ocean. Fish samples were collected fortnightly between June-2018 to February-2019 from the commercial boats operating bottom trawl nets with a cod-end mesh size of 35mm. The total length (L) and the wet weight (W) to the nearest 0.1 cm and 0.01 g, respectively which is followed by regression analysis. The values of exponent (b) for LWRs varied from 2.5803 (Parachaeturichthys polynema) to 3.4432 (Ostorhinchus oxina). Similarly, a value varied between 0.0037 (Bleekeria kallolepis) and 0.0258 (Archamia bleekeri). As per FishBase, a new TLmax has been recorded for four species such as Ostorhinchus oxina, Jaydia striata, Bleekeria kallolepis and Cocotropus roseus.