A MINOR MICROTUBULE-ASSOCIATED PROTEIN IS RESPONSIBLE FOR THE STIMULATION OF VESICULAR STOMATITIS-VIRUS TRANSCRIPTION INVITRO

An activity found in bovine brain microtubule-associated proteins (MAPs) which stimulated vesicular stomatitis virus (VSV) transcription in vitro co-eluted from a gel filtration column (Sepharose CL-6B) with a minor MAP subset of an apparent M(r) of 100 000 to 250 000. The activity did not appear to be closely associated with MAPs 1, MAPs 2, tau or tubulin. Anti-MAPs 1 and anti-MAPs 2 IgG did not reduce or abolish the stimulatory activity. The bovine brain MAPs stimulatory activity was similar to that found in HeLa cell extracts: both were heat-resistant, and both co-purified with the MAPs fraction of cell extracts; also amounts of each which gave maximum stimulation when used separately did not give additional stimulation when combined. Fractions from the Sepharose CL-6B column that contained the greatest amount of stimulatory activity exhibited little or no cAMP-dependent or -independent kinase activity. The MAPs stimulatory activity required the presence of both L and NS polymerase subunits.