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Cbl (named after Casitas B-lineage Lymphoma) is a mammalian gene encoding several proteins involved in cell signalling and protein ubiquitination. Mutations to this gene have been implication in a number of human cancers, particularly acute myeloid leukaemia.
Additional recommended knowledge
In 1989 a virally encoded portion of the chromosomal mouse Cbl gene was the first member of the Cbl family to be discovered  and was named v-Cbl to distinguish it from normal mouse c-Cbl. The virus used in the experiment was a retrovirus known as Cas-Br-M, and was found to have excised approximately a third of the original c-Cbl gene from mice it was injected into. Sequencing revealed that the portion carried by the retrovirus encoded a tyrosine kinase binding domain, and that this was the oncogenic form as retroviruses carrying full-length c-Cbl did not induce tumour formation. The resultant transformed retrovirus was found to consistently induce a type of pre-B lymphoma, known as Casitas B-lineage lymphoma, in infected mice.
Full length c-Cbl has been found to consist of several regions encoding for functionally distinct protein domains:
Three mammalian homologues have been characterized, which all differ in their ability to function as adaptor proteins due to the differing lengths of their C-terminal UBA domains:
Interestingly, both c-Cbl and Cbl-b have orthologues in D. melanogaster (D-Cbl) and C. elegans (Sli-1), hinting at a long evolutionary path for these proteins.
Ubiquitination is the process of chemically attaching ubiquitin monomers to a protein, thereby targeting it for degradation. As this is a multi-step process, several different enzymes are involved, the final one being a member of the E3 family of ligases. Cbl functions as an E3 ligase, and therefore is able to catalyse the formation of a covalent bond between ubiquitin and Cbl's protein substrate - typically a receptor tyrosine kinase. The RING-finger domain mediates this transfer, however like other E3 ligases of the RING type no intermediate covalent bond is formed between ubiquitin and the RING-finger domain. The stepwise attachment of ubiquitin to the substrate receptor tyrosine kinase can lead to its removal from the plasma membrane and subsequent trafficking to the lysosome for degradation.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Cbl_gene". A list of authors is available in Wikipedia.|