FIGURE 2.

Effects of nucleotide changes within the putative HRV14 2C cre motif on viral growth. (A) Quantification of mutant virus growth in HeLa cells. Each HRV14 2C cre mutant is named according to the substituted nucleotide. The amino acid changes that follow the nucleotide mutations are indicated in parentheses after the mutation and those conserving the amino acid properties are marked by an asterisk. The frequency plot of amino acid residue conservation in 25 HRV-B serotypes is shown at the foot of Panel A (http://weblogo.berkeley.edu/). Quantification of virus growth was measured by immunofluorescence 12 h post-infection and expressed as the mean of positive cells per total cells and expressed relative to that of HRV14-WT. (B) Schematic representation of the putative HRV14 2C cre structure as predicted by MFOLD from nucleotides 4256 to 4303. Nucleotide substitutions at position 4277, 4278, 4279, and 4286 (corresponding, respectively, to A₁, A₂, R², and R³ positions within the consensus R¹NNNA₁A₂R²NNNNNNR³ sequence) are represented in bold. (C) Quantification of virus growth for HRV14-DM versus HRV14-WT. Measurements were conducted by immunofluoresence as described in A. (D) Schematic representation of 2C cre motif for HRV14-DM (nucleotides 4256–4303) following the introduction of 12 silent mutations (surrounded nucleotides) as predicted by MFOLD. None of the crucial positions within the consensus cre loop sequence were mutated, except one at position 4279 (A → G) known to be permissive for efficient HRV14 replication (A). (E) HeLa cells infected by HRV14-WT, HRV14-DM, or Mock. Infected positive cells were detected by immunofluorescence (IF).