The murine leukemia viruses are group/type VI retroviruses belonging to the gammaretroviral genus of the Retroviridae family.

[citation needed] Endogenous MLVs are integrated into the host's germ line and are passed from one generation to the next.

Stoye and Coffin have classified them into four categories by host specificity, determined by the genomic sequence of their envelope region.

The viral glycoproteins are expressed on the membrane as trimer of a precursor Env, which is cleaved into SU and TM by host furin or furin-like proprotein convertases.

The viral genome is a single stranded, positive-sense RNA highly folded, molecule of around 8000 nucleotides.

[citation needed] The genome includes a conserved RNA structural element called a core encapsidation signal that directs packaging of RNA into the virion;[7] the tertiary structure of this element has been solved using nuclear magnetic resonance spectroscopy.

These changes lead to the release of the surface glycoprotein (SU) and the conformational rearrangement of the transmembrane protein (TM).

After entering the cytoplasm, viral RNA is copied into a single dsDNA molecule by reverse transcriptase.

Immature particles are released from the cell with the help of cellular "ESCRT" machinery and then they undergo maturation as the viral protease cleaves the polyproteins.