The interaction between Nhp6B and Tup1p is biologically relevant.
(A) Nhp6 is necessary for glucose repression of the GAL1
promoter. RNA was prepared from the depicted strains carrying a
GAL1-LacZ fusion integrated at the GAL1 locus. JD53 was used as
wild-type parental strain (lanes 1 and 4). The ΔNHP6 strain was
derived from JD53 that lacks NHP6A and NHP6B (lanes 2 and 5). In the
strain ΔNHP6 + NHP6 (lanes 3 and 6), NHP6A and NHP6B had been
reintegrated into the original loci. Equal amounts of total RNA were
loaded as confirmed by ethidium bromide staining (not shown) and
background hybridization to the 28 S rRNA (Right). The
Northern blot was probed with a LacZ probe (lanes 1–3) and with an
ACT1 probe (lanes 4–6). We consistently saw a slight increase in the
level of ACT1 mRNA in the ΔNHP6 strain. (B) Nhp6 is
not necessary for α2p repression. RNA was prepared from the depicted
strains, and the Northern blot was probed with an MFA1 probe
(Upper) or with an ACT1 probe (Lower). In
lane 1, RNA was isolated from JD52, a MATa strain. In lane 2, RNA was
isolated from JD53, which was used as wild-type parental MATα strain.
Lane 3 contained RNA from JD53 lacking NHP6A and NHP6B (ΔNHP6). For
lane 4, NHP6A and NHP6B had been reintegrated into the original loci
(ΔNHP6 + NHP6). Lane 5 contained RNA from JD53 lacking TUP1
(ΔTUP1). (C) NHP6 and REG1 deletions are synthetically
lethal. Shown are serial dilutions of the depicted S.
cerevisiae strains carrying a URA3-marked Nhp6B expression
plasmid (YCplac33-NHP6B) on medium lacking or containing FOA.