The structure and conservation of Pam. (A) Amino acid sequence of human Pam predicted from overlapping cDNA clones. The sequence includes the following motifs: LZ1 and LZ2, potential leucine zippers; RHD-1 and RHD-2, RCC1 homology domains; PR1 and PR2, Pam repeats; CDSM, cell division sequence motif; Myc-binding Region, insert in the original phage λgt11-PAM0; HHD, histone-binding protein homology domain; NLS, putative nuclear localization signal; RZF, potential ring zinc finger domain; and Zn, two putative C2H2-type zinc finger motifs. (B) Topography of human Pam. All abbreviations are as in A, except for SR, a serine-rich region occupying residues 2643–3057 (20% serine).