CHO CELLS PROVIDE ACCESS TO NOVEL N-GLYCANS AND DEVELOPMENTALLY-REGULATED GLYCOSYLTRANSFERASES

Chinese hamster ovary (CHO) cells express only a subset of the glycosy ltransferase activities known to exist, They do not express several fu cosyltransferases, galactosyltransferases, sialyltransferases or N-ace tylglucosaminyltransferases, However, following mutagenesis or transfe ction with large amounts of DNA, rare mutants that express a transfera se activity de novo have been obtained, The first CHO mutant of this t ype was LEC10, which expresses the N-acetylglucosaminyltransferase, Gl cNAc-TIII, that adds the bisecting GlcNAc to complex N-glycans, Severa l analogous gain-of-function mutants have now been characterized and, all express a new glycosyltransferase activity, In several cases, expr ession is known to reflect gene activation at the transcriptional leve l, Thus, CHO cells contain quiescent glycosyltransferase genes that ma y be activated by mutational events, Several of these transferases hav e properties distinct from previously described enzymes, In fact, the most recently characterized dominant CHO mutants, LEC14 and LEC18, eac h express a GlcNAc-T activity that creates novel N-glycans never befor e observed in glycoproteins from any other source, In these and possib ly other cases, it appears the CHO genome has provided access to new G lcNAc-Ts that may be difficult to identify by conventional methods.