Latent membrane protein1 (LMP1) encoded by the LMP1 gene of the Epstein-Barr virus (EBV) is a transmembrane protein, which can activate a number of cellular signal cascades and transcriptional factors leading to cell transformation. In the present study the sequencing of full-length LMP1 variants isolated from Russian patients with Hodgkin's lymphoma (HL), non-Hodgkin's lymphomae (NHL) and infectious mononucleosis (IM) has been carried out. The phylogenetic analysis of obtained sequences revealed dominance of the LMP1 variants belonging to proteins of low-divergent group LMP1-B95.8b characterized by minimal set of mutations. Investigation of biological properties in the Russian representatives of this group revealed that expression of studied LMP1 variants in embryonic kidney 293 cells was accompanied by insignificant increase in transcriptional factor NF-kappaB activation and had minor influence on activation of transcriptional factor AP-1. It was also detected that all investigated low-divergent LMP1 variants expressed in Rat-1 cells induced activation of inducible NO-synthase (iNOS) and intracellular production of nitric oxide (NO). At the same time the level of NO accumulation was lower than that induced by the low-transforming prototype variant LMP1-B95.8. The data obtained indicate that the LMP1 variants, which are the most common among Russian patients with EBV-associated lymphoproliferative diseases, are characterized by minimum number of mutations and rather low ability to activate basic cellular signaling pathways regardless the nature of pathological process, benign (IM) or malignant (HL, NHL). It is suggested that in addition to the modest activation of NF-kappaB and iNOS induction by LMP1 other factors are involved in the cell transformation process.