Table I. Amino acid changes in spt16 alleles.
| Allele | Amino acid changes | Phenotypes | Relative HO expression (% WT) | |||||
|---|---|---|---|---|---|---|---|---|
| 37°C | Spt | 6-AU | HU | A364a (genomic) | A364a (plasmid) | W303 (genomic) | ||
| SPT16-WT | ++ | ++ | ++ | ++ | 100 | 100 | 100 | |
| spt16-1, –2, –10 | G132D | – – | – – | – | ++ | 100 | 96 | 36 |
| spt16-4 | P565S P570L | – – | – – | – | ++ | 100 | ||
| spt16-6 | P920L | – – | – | ++ | ||||
| spt16-7 | T848I T849I D850Y | – – | – – | – | ++ | 86 | ||
| spt16-8 | G369D R373T | – – | – – | ++ | ++ | 85 | ||
| spt16-9 | G132D G836S P838S | – – | – – | – – | 40 | |||
| spt16-9a | G836S P838S | ++ | – – | |||||
| spt16-9b | G836S | ++ | ++ | |||||
| spt16-9c | P838S | ++ | ++ | |||||
| spt16-11 | T828I P859S | – – | – – | +/– | – | 114 | ||
| spt16-12 | A417T G568S R569K P599L | – – | ++ | ++/– | ++ | 107 | ||
| spt16-16 | R204W A273V C290V D318N R801Q A802T | – – | – – | – –/+ | 50 | |||
| spt16-16a | R204W A273V C290V D318N | – – | – – | – –/+ | ||||
| spt16-16b | R801Q A802T | ++ | ++ | ++ | ||||
| spt16-24 | T434I | – | – – | ++ | ++ | 63 | ||
Sequencing of the SPT16 ORF from mutants revealed the predicted amino acid changes shown. Phenotypes were tested either in strains lacking the genomic SPT16 and containing a mutant allele on a plasmid (for growth at 37°C, the Spt– phenotype and sensitivity to HU) or in strains in which the spt16 allele was integrated into the genome (for testing sensitivity to 6-AU). Effects were scored from ++ (WT) to – (mutant). HO mRNA was measured as in Figure 2.