A mammalian cell/E.coli shuttle vector. Confers selective advantage to mammalian cell lines grown in the presence of methotrexate. Selectable marker in dhfr- cell culture strains. (ATCC staff) Restriction digests analyzed on agarose gels give the following sizes (kb): BamHI--5.2; PvuII/HindIII--4.8, 0.3; BglII/EcoRI--3.6, 1.5; AccI/HindIII--3.6, 0.54, 0.44, 0.27; AccI--3.6, 0.96, 0.27; HindIII--5.0; PstI--4.1, 0.9. (ATCC staff) Restriction digests of the clone give the following sizes (kb): EcoRI--4.8; HindIII--4.8; BamHI--4.8. (ATCC staff) Medium is 1227 LB plus ampicillin. Hosts: E.coli HB101, E.coli MC1061, vertebrate cells, E.coli.