Note that the molecular mass of PmFKBP46 protein expressed in E. coli and in shrimp hemocytes were all higher than the estimated molecular weight based on its deduced amino acid sequence, suggesting some posttranslational modification and/or highly charged nature of the protein. PmFKBP46 protein was also detected in shrimp gill lysates . A transcription expression study by RT-PCR also indicated the presence of PmFKBP46 transcripts in shrimp hemocytes and gills as well as other tested organs such as the hepatopancreas, intestine, lymphoid organ and stomach . To add more evidence supporting their interaction, the location of PmFKBP46 and VP15 was investigated by indirect immunofluorescence assay in healthy and WSSV-infected shrimp . In situ immunocytochemistry by confocal microscopy using anti-VP15 and anti-PmFKBP46 antibodies , revealed that fluorescence for PmFKBP46 was evenly distributed in the nuclei of normal hemocytes while there was no fluorescence for VP15. By contrast , PmFKBP46 and VP15 were co-localized in the nuclei of hemocytes from WSSV-infected shrimp. In addition, the PmFKBP46 signal intensity appeared to be slightly increased in the presence of WSSV. Control staining experiments performed using i) preimmune serum alone, ii) each HSC primary antibody alone, and iii) secondary antibodies alone did not yield any signal in the hemocytes, excluding the possibility of cross-reactivity between tested antibodies and hemocyte proteins . Similar immunocytochemistry tests performed using Sf-9 cells cotransfected with PmFKBP46-V5 and VP15-FLAG recombinant plasmids also revealed both proteins co-localized in the nuclei . All these experimental results suggested that VP15 and PmFKBP46 shared the same subcellular location both in vitro and in vivo and supported the proposal that interaction between PmFKBP46 and VP15 was genuine. The nuclear localization of PmFKBP46 and the presence of a putative helix-loop-helix in the deduced protein (+)-JQ1 Epigenetic Reader Domain inhibitor sequence raised the possibility that it might have DNA binding activity similar to that previously reported for VP15 .