Retinoblastoma essays

Retinoblastoma essays The retinoblastoma families of proteins are key cell cycle regulatory molecules important for the differentiation of various mammalian cell types. The retinoblastoma protein (RB) regulates transcription of a variety of genes either by blocking the activation domain of various activators or by active repression (finding of appropriate promoters). If the RB's function is lost, it will lead to a variety of cancers and defects in the development of certain cell types. Phosphorylation of RB by cyclin and cyclin-dependent kinases leads to dissociation of RB from E2F (protein receptor), allowing progression into the S-phase. RB has also been proven to have the ability to block cell cycle progression from G1- to the S-phase. (Chan et al, 2001) RB is also a general tumor suppressor, which is associated with a central N (A/B) and C-terminal (pocket domains, which are binding sites for RB) that were defined to have the ability to bind cellular and viral proteins that affect the cell division cycle. Mutations in the pocket domain region are often tumorigenic. These pocket domains are also present in homologues structures of RB that exhibit similar protein binding and functional characteristics pertaining to the cell division cycle. Even though these structures bind to other proteins and have conspicuous molecular and cellular characteristics, they both have the ability to restrain cell growth by inhibiting the pocket domain-binding E2F family of transcription factors. These factors are crucial for the expression of genes that are vital for the S-phase of the cell division cycle. (Singh et al, 2001) Nuclear receptors (NRs) represent a super family of structurally and functionally related ligand-inducible transcription factors that deal with different biological events such as development, differentiation, and homeostasis. Members of this family include receptors for thyroid hormones, steroids, and vitamin D. (Chan et al., 2001) ...