Evidence for a regulatory element controlling amino aced transport system L in Chinese hamster ovary cells

✍ Scribed by Dr. Ellen J. Collarini; George S. Campbell; Dale L. Oxender

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 583 KB
• Volume: 56
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.240560415

✦ Synopsis

Abstract

We have used the technique of somatic cell hybridization to study the regulation of the neutral amino acid transport system L in Chinese hamster ovary (CHO) cells. The cell line CHO–;__ts__O25C1 has a temperature‐sinsitive mutationin leucyl‐tRNA synthetase. At the nonpermissive temperature of 39^o^C, CHO–__ts__O25C1 cells are unable to charge leucyl‐tRNA and behave as though starved for leucine by increasing their system L transport activity two‐ to fourfold. From the temperature‐sensitive cell line, we have isolated a regulatory mutant cell, CHO–C11B6, that has constitutively elevated system L transport activity. The CHO–C11B6 cell line retains the temperature‐sensitive leucyl‐tRNA synthetase mutation, but growth of this cell line is temperature resistant because its increased system L transport activity leads of increased intracellular leucine levels, which compensate for the defective. Hybrid cells formed by fusion of the temperature‐sensitive CHO–;__ts__O25C1 cells the temperature‐resistant CHO–C11B6 cells show temperature‐sensitive growth and temperature‐dependent regulation of leucine transport activity. These data suggest that the system L activity of CHO cells is regulated by a dominant‐acting element that is defective or absent in the regulatory mutant CHO–C11B6 cell line.