The WB and UPN networks are shutting down at the end of the summer, and a new network, CW, will launch. CW will be owned by CBS (UPN’s owner), Tribune Co. and Warner Bros. (Tribune and Warner owned the WB.) In San Francisco, CBS-owned UPN44 will become the CW affiliate. KBWB Channel WB20 will lose its network affiliation and its source of two hours of primetime programming. AP’s report.