Av. Strunnikov et al., SMC1 - AN ESSENTIAL YEAST GENE ENCODING A PUTATIVE HEAD-ROD-TAIL PROTEIN IS REQUIRED FOR NUCLEAR DIVISION AND DEFINES A NEW UBIQUITOUS PROTEIN FAMILY, The Journal of cell biology, 123(6), 1993, pp. 1635-1648
The smc1-1 mutant was identified initially as a mutant of Saccharomyce
s cerevisiae that had an elevated rate of minichromosome nondisjunctio
n. We have cloned the wild-type SMC1 gene. The sequence of the SMC1 ge
ne predicts that its product (Smc1p) is a 141-kD protein, and antibodi
es against Smc1 protein detect a protein with mobility of 165 kD. Anal
ysis of the primary and putative secondary structure of Smc1p suggests
that it contains two central coiled-coil regions flanked by an amino-
terminal nucleoside triphosphate (NTP)-binding head and a conserved ca
rboxy-terminal tail. These analyses also indicate that Smc1p is an evo
lutionary conserved protein and is a member of a new family of protein
s ubiquitous among prokaryotes and eukaryotes. The SMC1 gene is essent
ial for viability. Several phenotypic characteristics of the mutant al
leles of smc1 gene indicate that its product is involved in some aspec
ts of nuclear metabolism, most likely in chromosome segregation. The s
mc1-1 and smc1-2 mutants have a dramatic increase in mitotic loss of a
chromosome fragment and chromosome III, respectively, but have no inc
rease in mitotic recombination. Depletion of SMC1 function in the ts m
utant, smc1-2, causes a dramatic mitosis-related lethality. Smc1p-depl
eted cells have a defect in nuclear division as evidenced by the absen
ce of anaphase cells. This phenotype of the smc1-2 mutant is not RAD9
dependent. Based upon the facts that Smc1p is a member of a ubiquitous
family, and it is essential for yeast nuclear division, we propose th
at Smc1p and Smc1p-like proteins function in a fundamental aspect of p
rokaryotic and eukaryotic cell division.