UNIT 16.12 Transient Expression of Proteins Using COS Cells

  1. Alejandro Aruffo

Published Online: 1 NOV 2002

DOI: 10.1002/0471142727.mb1612s60

Current Protocols in Molecular Biology

Current Protocols in Molecular Biology

How to Cite

Aruffo, A. 2002. Transient Expression of Proteins Using COS Cells. Current Protocols in Molecular Biology. 60:III:16.12:16.12.1–16.12.7.

Author Information

  1. Bristol-Myers Squibb, Princeton, New Jersey

Publication History

  1. Published Online: 1 NOV 2002
  2. Published Print: OCT 2002


This unit describes the use of COS cells to efficiently produce a desired protein in a short period of time. These cells express high levels of the SV40 large tumor (T) antigen, which is necessary to initiate viral DNA replication at the SV40 origin. Each COS cell transfected with DNA encoding a cell-surface antigen (in the appropriate vector) or cytoplasmic protein will express several thousand to several hundred thousand copies of the protein 72 hr posttransfection. If the transfected DNA encodes a secreted protein, up to 10 mg of protein can be recovered from the supernatant of the transfected COS cells 1 week posttransfection. COS cell transient expression systems have also been used to screen cDNA libraries, to isolate cDNAs encoding cell-surface proteins, secreted proteins, and DNA binding proteins, and to test protein expression vectors rapidly prior to the preparation of stable cell lines.