FIG. 2.

Schematic diagrams of the genomic regions containing the principal replication genes of phages T4 and RB49. (A) Diagrams of the T4 and RB49 loci containing the genes encoding the DNA polymerase and the accessory replication proteins. A box proportional to the length of the coding sequence represents each gene in the region. The name of the gene is indicated either inside the corresponding box or just below it. A stippled box indicates a putative RB49 gene lacking homology to all entries in the database. A grey box represents a gene in RB49 with a homologue in T4. The percentage of amino acid identity of the RB49 protein to the corresponding T4 homologue is indicated below the grey boxes. A box with a broken end indicates that the sequence of the corresponding gene is not complete. The black boxes identify the T4 genes that are absent from the RB49 sequence. The thin grey (RB49) and black (T4) lines that connect the boxes depict the intergenic spacer sequences. These lines are differently shaded to indicate that they have little nucleotide sequence homology. The bent arrowheads indicate the positions of the promoters in this region, and they are oriented in the direction of their transcription. The temporal class of each promoter is marked above the arrow (E, early promoters; M, Middle promoters; L, late promoters). If this letter is circled, the function of the corresponding promoter in RB49 has been confirmed by 5′-end mapping of the transcripts. The sequence of this region of the RB49 genome was obtained from two different PCR products. The first product was obtained with the primers 49gp460 and 49gp43.21, while the second PCR product was obtained with primers 49gp6111 and 49gp43.18 (see Table 1 for the primer sequences). The sequences of these oligonucleotides were based on the random clones that were identified in this work as having homology to gene 46, gene 43, and gene 61. These sequences have been deposited in EMBL/GenBank with accession number AF410869. (B) Diagrams of the gene 32 region of the genome of phages T4, T2, and RB49. The notation is the same as used in the panel above. The T2 gene 32 sequence has been determined (50), but the remainder of the operon has only been characterized by partial sequencing and PCR analysis (47). For the T2 sequence, the small dotted line depicts the intergenic spacer between gene 32 and gene 59 whose the nucleotide sequence is completely different from that of T4 (47). The black lines at the extremity of the T2 locus indicate that we have not compared these sequences in T2 and T4. The sequence of this region of the RB49 genome was obtained from two different overlapping PCR products. The first product was obtained with the primers 49gp341 and 49gp321 (see Table 1 for the primer sequences), while the second PCR product was obtained with primers 49gpnrdA1 (based on the RB49 gene nrdA sequence obtained previously by Monod et al. [54]) and 49gp32.2 (based on a random clone analyzed in this work). These sequences have been deposited in EMBL/GenBank with accession number AF410870.