The group's main interest is the regulation of cell cycle events in the fission yeast, Schizosaccharomyces pombe. At present, we concentrate on events in G1 phase, particularly those regulating entrance into S phase.
In our work, we employ standard molecular biological methods, different cell synchronization techniques, flow cytometry, fluorescence microscopy of tagged proteins, and a wide set of in vitro assays.

We collaborate with the neighbouring group of this department, working with bacterial cell cycle control, and with several other groups in Europe.

We have developed and refined several methods to study the G1/S transition in yeast: cdc10ts and cdc25ts block-and-release, centrifugal elutriation, flow cytometry, spore germination. Our experiments have demonstrated that fission yeast do not have a classical checkpoint response to UV irradiation in G1. Entry into S phase is delayed after UV irradiation in G1, but this pathway does not involve the classic checkpoint pathways that target Cdc2 phosphorylation (Nilssen et al, PNAS 2003). Our conclusions rest on investigations of the firing of early origins of DNA replication (2D gel analyses) and of the formation of pre-replication complexes (pre-RC) after labelling MCM proteins with green fluorescent protein (GFP).

The cell-cycle delay occurs in G1 and is totally dependent upon the kinase Gcn2 (Tvegård et al, 2007). Induction of the checkpoint is always followed by phosphorylation of the translation initiation factor eIF2α and by a dramatic inhibition of translation. The checkpoint is induced by the DNA-damaging agents ultraviolet light (UVC), methyl methane sulfonate (MMS) and hydrogen peroxide (H2O2), but not by other DNA-damaging agents, such as ionising radiation and treatment with psoralen plus long-wavelength UV light (Krohn et al, 2008). This evidence shows that the checkpoint is not induced by DNA damage in general.

Current work focus on identifying the signalling pathway that activates Gcn2, the targets of Gcn2 in fulfilling its checkpoint function and the mode of translation inhibition after Gcn2 activation.

Grallert B, Nurse P (1996)
The ORC1 homolog orp1 in fission yeast plays a key role in regulating onset of S phase
Genes Dev, 10 (20), 2644-54
PubMed 8895665

Carlson CR, Grallert B, Bernander R, Stokke T, Boye E (1997)
Measurement of nuclear DNA content in fission yeast by flow cytometry
Yeast, 13 (14), 1329-35
PubMed 9392077

Carlson CR, Grallert B, Stokke T, Boye E (1999)
Regulation of the start of DNA replication in Schizosaccharomyces pombe
J Cell Sci, 112 ( Pt 6), 939-46
PubMed 10036243

Grallert B, Kearsey SE, Lenhard M, Carlson CR, Nurse P, Boye E, Labib K (2000)
A fission yeast general translation factor reveals links between protein synthesis and cell cycle controls
J Cell Sci, 113 ( Pt 8), 1447-58
PubMed 10725227

Synnes M, Nilssen EA, Boye E, Grallert B (2002)
A novel chk1-dependent G1/M checkpoint in fission yeast
J Cell Sci, 115 (Pt 18), 3609-18
PubMed 12186947

Nilssen EA, Synnes M, Kleckner N, Grallert B, Boye E (2003)
Intra-G1 arrest in response to UV irradiation in fission yeast
Proc Natl Acad Sci U S A, 100 (19), 10758-63
PubMed 12960401

Tvegård T, Soltani H, Skjølberg HC, Krohn M, Nilssen EA, Kearsey SE, Grallert B, Boye E (2007)
A novel checkpoint mechanism regulating the G1/S transition
Genes Dev, 21 (6), 649-54
PubMed 17369398

Krohn M, Skjølberg HC, Soltani H, Grallert B, Boye E (2008)
The G1-S checkpoint in fission yeast is not a general DNA damage checkpoint
J Cell Sci, 121 (Pt 24), 4047-54
PubMed 19033384