Increased ribonucleotide reductase activity in hydroxyurea-resistant mosquito cells

Hydroxyurea-resistant Aedes albopictus mosquito cells were selected by incr emental exposure of unmutagenized cells to hydroxyurea concentrations rangi ng from 0.1 to 8 mM, Clonal populations that had become 40-fold more resist ant to hydroxyurea than wild-type cells varied in morphology, and their gro wth rate decreased to a similar to 45 h doubling time, relative to an 18 h doubling time in unselected cells. At this level of resistance, the cells r emained diploid, with a modal chromosome number of 6, When labelled with S- 35[methionine/cysteine], clone HU1062, which grew in the presence of 8 mM h ydroxyurea, overproduced a labeled protein with the approximate size of the 45,000 dalton M2 subunit of ribonucleotide reductase, Consistent with this observation, ribonucleotide reductase activity in HU-1062 cells was approx imately 10-fold higher than in wild-type control cells. This is the first e xample of an hydroxyurea-resistant insect cell line. (C) 1997 Wiley-Liss, I nc.