RETRACTION
Volume 15, no. 3, p. 1545–1553, 1995, https://doi.org/10.1128/MCB.15.3.1545. The publisher hereby retracts this article. Questions have been raised by concerned readers about the integrity of the data. The American Society for Microbiology has reviewed the figures and confirmed evidence of apparent manipulation and duplication. Since the integrity of the data as presented was compromised, this publication is retracted in its entirety. We apologize to the readers of Molecular and Cellular Biology and regret any inconvenience that this causes. The authors did not agree to this retraction.