2005 Volume 74 Issue 3 Pages 85-93
Members of the Y-box-binding protein family regulate gene expression through both transcription and translation. Bombyx Y-box-binding protein (BYB) was found to enhance the binding activity of various transcription factors including fibroin-modulator-binding protein-1 (FMBP-1) to their target DNA sequences. We dissected BYB and analyzed the regions responsible for the enhancement. Enhancement of protein-DNA interaction by BYB was conducted independently by the conserved cold shock domain (CSD) in the N-terminal half and by the C-terminal half containing basic/aromatic (B/A) islands that are rich in arginine and aromatic residues. Expression of BYB was analyzed from the penultimate to last instar during larval development. BYB was expressed in every tissue examined, but controlled differentially. The expression pattern was comparatively dependent on the molting cycle in the carcass, fat body and anterior silk gland (ASG); the expression decreased during the fourth molt. However, in the middle silk gland (MSG) and posterior silk gland (PSG), the expression increased steadily from the fourth instar to early into the fifth instar. The results suggested that BYB exhibits tissue- and stage-dependent function (s) during larval development.
