BOVINE LEUKEMIA VIRUS GENES

The review presents information on the functions of bovine leukemia genes. Bovine leukemia virus is the cause of bovine leukemia and a malignant form of B-cell lymphoma. BLV infection is one of the most common chronic diseases of farm animals. The main symptom of leukemia is the malignant proliferation of hematopoietic cells with impaired maturation, resulting in diffuse infiltration of organs by these cells or the appearance of tumors. All retroviruses are encoded by the gag, pro, pol, and env genes, which are necessary for the production of infectious virions, and are flanked by two identical long terminal repeats. The gag, pro, pol, and env genes in retroviruses encode internal structural proteins of the virion, viral protease, reverse transcriptase, and glycoproteins of the virion envelope, respectively. The gag gene is highly conserved and is responsible for encoding three major non-glycosylated proteins: the nucleocapsid protein p12 (which binds to the viral genomic RNA), the matrix protein p15 (which binds to the viral genomic RNA and interacts with the lipid bilayer of the viral membrane), and the nucleocapsid protein p24 (which serves as the main target of the host immune response). The env gene encodes two glycosylated proteins: the envelope protein gp51 and the transmembrane protein gp30, which facilitate virus-cell fusion through interaction with cell membrane receptors. The env gene encodes the surface gp51 and transmembrane gp30 glycoproteins, which play a key role in virion morphogenesis. They are responsible for tropism to cellular epitopes and for virus penetration into cells and are involved in cell fusion and syncytia formation. Stable conservatism of six gp51 sequences of virus isolates with different geographic localizations was established. Regulatory proteins are important for regulating viral transcription, causing malignant transformation of tumors and release of viral infection, while auxiliary proteins R3 and G4 help maintain a high viral load.