BLCAP
Bladder cancer-associated protein is a protein that in humans is encoded by the BLCAP gene.
Function
BLCAP was identified using a differential display procedure with tumor biopsies obtained from a noninvasive and an invasive bladder transitional cell carcinoma. Although database searches revealed no homology to any human gene at the time of identification, mouse, rat and zebrafish orthologs have since been identified. The protein appears to be down-regulated during bladder cancer progression.The protein also known as BC10 is an 87-amino-acid-long protein, but its biological functions are largely unknown. However it is a widely believed that the protein is involved in tumour suppression by decreasing cell growth through initiating apoptosis. It is widely expressed protein but expression is particularly high in brain and B lymphocytes. Alternative promoters and alternative splicing allow the protein to exist as several different transcript variants. This number is further increased as the pre-mRNA of this protein is subject to several RNA editing events.
Structure
The structure of the protein is predicted to be a globular protein with 2 transmembrane domains.RNA editing
The human BLCAP gene is composed of two exons which are separated by an intron. Exon 1 of the gene encodes a 5′ sequence of the 5′UTR while exon 2 includes the remaining sequence of the 5′UTR, the coding region and the 3′UTR. The coding sequence of the BLCAP gene is therefore intronless.Type
A to I RNA editing is catalyzed by a family of adenosine deaminases acting on RNA that specifically recognize adenosines within double-stranded regions of pre-mRNAs and deaminate them to inosine. Inosines are recognised as guanosine by the cells translational machinery. There are three members of the ADAR family ADARs 1-3 with ADAR 1 and ADAR 2 being the only enzymatically active members.ADAR3 is thought to have a regulatory role in the brain. ADAR1 and ADAR 2 are widely expressed in tissues while ADAR 3 is restricted to the brain. The double stranded regions of RNA are formed by base-pairing between residues in the close to region of the editing site with residues usually in a neighboring intron but can be an exonic sequence. The region that base pairs with the editing region is known as an Editing Complementary Sequence.Location
The editing sites are all concentrated together between the last 150 nucleotides of intron 1 and the beginning of exon 2. There are 17 identified editing sites in total in the pre-mRNA of this protein. Of these, 11 are found within the intronic sequence, 3 are in the 5'UTR region while 3 are found within the coding sequence. Some of these editing sites occur in the highly conserved amino terminal of the protein.The Y/C editing site is located at amino acid 2 of the final protein. The codon change introduces a tyrosine to a cysteine substitution.
The Q/R site is a second coding region found at amino acid 5 of the final protein. Here the glutamine is codon is converted to an arginine.
The third K/R editing site within the coding sequence is found at amino acid position 15 of the final protein where a Lysine is converted to an Arginine.
The ECS is predicted to be found in the intron with the double stranded structure formed containing all 17 of the editing sites. It is likely since all the editing sites fall within the duplex region that editing occurs in exonic and intronic sequences at the same time. There is a high level of conservation of the last 150 nucleotides of the intronic region and the start of exon 2.