Identification of a novel bone morphogenetic protein (BMP)-inducible transcript, BMP-inducible transcript-1, by utilizing the conserved BMP-responsive elements in the Id genes.

Bone morphogenetic proteins (BMPs) inhibit myogenesis and induce osteoblastic differentiation in myoblasts. They also induce the transcription of several common genes, such as Id1, Id2 and Id3, in various cell types. We have reported that a GC-rich element in the Id1 gene functions as a BMP-responsive element (BRE) that is regulated by Smads. In this study, we analyzed and identified BREs in the 5'-flanking regions of the mouse Id2 and Id3 genes. The core GGCGCC sequence was conserved among the BREs in the Id1, Id2 and Id3 genes and was essential for the response to BMP signaling via Smads. We found a novel BRE on mouse chromosome 13 at position 47,723,740-47,723,768 by searching for conserved sequences containing the Id1 BRE. This potential BRE was found in the 5'-flanking region of a novel gene that produces a non-coding transcript, termed BMP-inducible transcript-1 (BIT-1), and this element regulated the expression of this gene in response to BMP signaling. We found that BIT-1 is expressed in BMP target tissues such as the testis, brain, kidney and cartilage. These findings suggest that the transcriptional induction of the Ids, BIT-1 and additional novel genes containing the conserved BRE sequence may play an important role in the regulation of the differentiation and/or function of target cells in response to BMPs.