HUMAN ADENOVIRUS TYPE-41 CONTAINS 2 FIBERS

DNA sequencing of the subgroup F human adenovirus serotype 41 (TAK, Ad 41) fiber gene revealed the presence of two adjacent open reading fram es encoding information for proteins with molecular weights of 60.6 kD a and 41.4 kDa (Pieniazek, et al; Nucleic Acids Res, 18: p. 1901, 1990 ). In this paper, various approaches were used to characterize the two proteins and determine whether both fibers were expressed in infected cells as well as on viral particles. We initially used a reverse tran scriptase-polymerase chain reaction with primers for the short and lon g fiber genes to amplify mRNA from Ad41 infected HEp-2 cells at 48 h p ost-infection. Two distinct DNA bands; one slightly larger than 1.1 kb p and the other at about 1.7 kbp were identified. Second, we used poly clonal anti-Ad41 virion and monoclonal anti-Ad5 fiber antibodies to de monstrate that at both 24 and 36 h post-infection, Ad41 expressed two fiber proteins of the expected size. Specifically, by SDS-PAGE, one fi ber (short) had a molecular weight of 40 kDa, while the other (long) h ad a molecular weight of 60 kDa. Third, by electron microscopy, two si zes of fibers were released from CsCl purified virions, both having a characteristic adenovirus morphology, with a knob at one end. The long fiber measured 315 Angstrom in length and the short fiber was 250 Ang strom long. These measurements are consistent with the two Ad41 fibers being encoded by the above open reading frames. We also performed a c omputer search to compare fiber sequences from other human adenovirus serotypes with that of the Ad41 short and long fiber proteins. The pri mary structure of both Ad41 fibers were found to be similar in that th ey contained tail, shaft and knob regions. Further, the tail region of both fibers (amino acids 1-42) showed a 74% overall homology to each other and contained the Ad conserved sequence NH2-F-N-P-V-Y-P-Y-COOH. An interesting difference, however, was observed in the shaft region w here the long fiber (amino acids 43-389) had twenty-two 16-amino acid repeat motifs, while the short fiber (amino acids 43-233) had only twe lve. Finally, we noted that the long fiber knob region was about 15% l onger than that of the short fiber, and showed little overall homology . In conclusion, human adenovirus subgroup F (type 41) virions appear to differ from those of all other human adenoviruses (subgenera A-E) i n that they contain two fiber genes and correspondingly, two different sized fibers. A recent paper (Kidd et al., Virology 192: 73-84, 1993) came to a similar conclusion for Ad40, another subgenus F virus.