Fission Yeast Pot1-Tpp1 Protects Telomeres and Regulates Telomere Length

Research areas: chromatin, DNA, antibody research

In yeast, Tpz1 forms a complex with POT1 (Protection of Telomeres). Tpz1 is the yeast homologue of mammalian TPP1. It binds to Ccq1 and the newly discovered protein Poz1 (Pot1-associated in Schizosaccharomyces pombe), both of which protect telomeres and regulate telomerase. Telomeres constitute a buffer zone at each end of a chromosome to protect the coding sequence in their midst. In mammals, Pot1 binds to the telomeric G-rich DNA overhang. By this it protects the telomeric DNA and regulates telomerase. Mammalian Pot1 interacts with TPP1 and together they make up a part of the six-protein shelterin complex.

The yeast Pot1-Tpz1 complex performs its functions by recruiting the effector molecules Ccq1 and Poz1. Poz1 bridges Pot1-Tpz1 and Taz1-Rap1 and by this connects the single-stranded and double-stranded telomeric DNA regions.

Such molecular architectures resemble the one of mammalian shelterin, suggesting that the general DNA-protein architecture has been conserved throughout evolution.

Source:

Tomoichiro Miyoshi et al.: Fission Yeast Pot1-Tpp1 Protects Telomeres and Regulates Telomere Length, Science 320, 1341 – 1344 (06. June 2008)

The Transcription/Migration Interface in Heart Precursors of Ciona intestinalis

Research areas: signalling, transcription factors, antibody research

Fibroblast growth factor signalling and the forkhead transcription factor FoxF upregulate the small guanosine triphosphatase RhoDF by direct interaction. RhoDF synergises with Cdc42 and together they support the protrusive activity of migrating cells, as a research team from the University of California discovered. They report that RhoDF can trigger membrane protrusions without the aid of any other cellular activities that are required for migration. They assume that the transcriptional regulation of specific effector genes affects the coordinated deployment of discrete cellular modules underlying migration.

The scientists used techniques like cell sorting, microarrays, and targeted molecular manipulations to analyse cardiac cell migration in the ascidian Ciona intestinalis. Cardiac cells were chosen because they regulate genes involved in most cellular activities required for migration, including adhesion, cell polarity, and membrane protrusions.

RhoDF is part of the Rho antibody protein family of which Rac is the founder, appearing already before Coelomates evolved. RhoDF and Rnd were found first in Chordates (A. Boureux et al., 2006).

Sources:

Lionel Christiaen et al.: The Transcription/Migration Interface in Heart Precursors of Ciona intestinalis, Science 320, 1349 - 1352 (06. June 2008)