Cell Cycle Regulated Gene Expression in Yeasts - Advances in Genetics - page 67

IV. CONSERVATION OF CONTROLS

A major reason for using yeasts to study fundamental biological problems is to
exploit the acquired knowledge to understand more complex organisms, espe-
cially humans. In many cases, molecular processes are so complicated in higher
eukaryotes that it is impossible to unravel and understand them, without prior
knowledge from more simple systems. In contrast, in yeasts, the relatively
simplicity of processes permits their characterization, with this information
permitting subsequent analysis and understanding in higher eukaryotes. It has
also been very useful to study the same process in both budding and fission yeasts,
as it has been observed that mechanisms conserved between these two distantly
related organisms, are often conserved in other eukaryotes (C ˆ te

et al. , 2009;

Forsburg, 1999; Forsburg and Nurse, 1991; Ukil , 2008).

Among the various genes transcribed at particular cell cycle times, a
number of genes have been shown to be periodically expressed in both budding
and fission yeasts (Table 2.2). Computational analyses have identified up to 20%
of cycling genes encode orthologs that are periodically expressed in both species,
with 5-7% in other eukaryotic organisms (B ¨ hler, 2005a; Lu

et al.

et al. , 2007).

Table 2.2. Cell Cycle Regulated Genes in Both Budding and Fission Yeasts

Cell cycle
phase

Human
ortholog Budding yeast Fission yeast Function

cdc22 þ G1-S RNR1 Ribonucleotide reductase Yes

cdc18 þ CDC6 Regulator of DNA replication Yes

mik1 þ SWE1 Protein kinase regulating

mitotic entry

Yes

cig2 þ CLB1-CLB6 B-type cyclins Yes

pol1 þ POL1 DNA polymerase Yes

cdc20 þ POL2 DNA polymerase e Yes

S phase Histone genes Histone genes Histones H2A, H2B, H3,

and H4

Yes

plo1 þ G2-M-G1

phases

CDC5 Polo kinase Yes

ark1 þ IPL1 AuroraB kinase Yes

fin1 þ KIN3 NimA kinase Yes

slp1 þ CDC20 APC regulator Yes

ace2 þ ACE2 Cell cycle transcription factor Yes

mid2 þ BUD4 Cytokinesis Yes

spo12 þ SPO12 Cell cycle regulator Not known

Representative genes from each cluster are shown, which have significant roles in cell cycle
controls and whose orthologs are also periodically expressed in mammalian cells.