Retroviridae Essay Example | Topics and Well Written Essays - 3000 words

Retroviridae - Essay Example Based on the similarities in amino acid sequences in the reverse transcriptase proteins of retroviruses (Coombs, Medscape, the retroviruses can be classified into: alpharetroviruses, betaretroviruses, gammaretroviruses, deltaretroviruses, epsilonretroviruses, lentiviruses and spuma-viruses (Table-1). The alpharetroviruses, betaretroviruses, and gammaretroviruses are considered simple retroviruses; the deltaretroviruses, epsilonretroviruses, lentiviruses, and spuma-viruses are considered complex (Coombs, Medscape). Avian sarcoma and leukosis viral group, mammalian B-type viral group, murine leukemia-related viral group, human T-cell leukemia–bovine leukemia viral and D-type viral group were formerly known as oncogenic retroviruses (Coffin, NCBI). Retroviruses are further classified into simple and complex categories based on the organization of their genomes. There are 3 major coding domains which are common to all the retroviruses. These domains have information for virion proteins. The domains are known as gag, pol and env. Gag directs the synthesis of internal virion proteins that form the matrix, the capsid, and the nucleoprotein structures. Pol contains the information for the reverse transcriptase and integrase enzymes and env contains information for the synthesis of the surface and transmembrane components of the viral envelope protein. In addition to all these major coding domains, there is one smaller coding domain common to all retroviruses. It is called pro and it codes for the virion protease. Simple retroviruses are those which carry only this elementary information. All oncogenic members except the human T-cell leukemia virus–bovine leukemia virus (HTLV-BLV) genus are simple retroviruses. Complex retrov iruses code for additional regulatory non-virion proteins derived from multiple spliced messages. The additional coding domains include tat, rev, etc.