Positioning of telomeres at the nuclear periphery can have dramatic effects on gene expression by establishment of heritable, transcriptionally repressive subdomains. However, little is known about the integral membrane proteins that mediate telomere tethering at the nuclear envelope. Here, we find a previously unrecognized function for the Saccharomyces cerevisiae Sad1-UNC-84 domain protein Mps3 in regulating telomere positioning in mitotic cells. Our data demonstrate that the nucleoplasmic N-terminal acidic domain of Mps3 is not essential for viability. However, this acidic domain is necessary and sufficient for telomere tethering during S phase and the silencing of reporter constructs integrated at telomeres. We show that this is caused by the role of the Mps3 acidic domain in binding and localization of the silent information regulator protein Sir4 to the nuclear periphery. Thus, Mps3 functions as an integral membrane anchor for telomeres and is a novel nuclear receptor for the Sir4 pathway of telomere tethering and gene inactivation.

Binding of histone H2A.Z to the SUN family member Mps3 is chromatin independent.

We report the attachment of alkyl residues to a gold surface through a tin atom. Covalent trialkylstannyl and trialkylsilyl salts of trifluoromethanesulfonic, trifluoroacetic, and p-toluenesulfonic acids containing one to three C(18)H(37) chains and two to no CH(3) groups in the molecule have been synthesized. They were tested for adsorption on gold from solution under ambient conditions using ellipsometry, FTIR spectroscopy, contact angle, and electrode-blocking measurements. All nine trialkylstannyl salts form similar stable monolayers with the loss of the acid residue and form no multilayers. The monolayers differ from those formed from alkanethiols. They are much thinner, less ordered, less hydrophobic, and only slightly electrode-blocking. Their stability to solvents, bases, acids, and reductants is somewhat lower than that of a 1-octadecanethiol monolayer, but their resistance to heat and oxidants, including air, is slightly better. The distinctive properties of these monolayers may be of interest in certain circumstances, but we expect the attachment of molecules to gold through a tin atom to be of the most value in work with single-molecule structures. The trialkylsilyl salts showed no tendency to adsorb onto gold under these conditions.

n-Alkyl self-assembled monolayers can be directly attached to gold through C−Au bonds by the deposition of organomercury salts on gold substrates, as shown here using nbutylmercury and n-octadecylmercury tosylate derivatives. The Hg atoms, which are codeposited during this process, are removed by thermal annealing at 95 °C, resulting in alkyl monolayers having a significantly enhanced thermal stability compared with alkanethiol monolayers, however, a lower degree of conformational order. The monolayer properties are elucidated by X-ray photoemission and IR spectroscopy, STM, ellipsometry, and contact-angle goniometry.

Treatment of a gold surface with a solution of C18H37HgOTs under ambient conditions results in the formation of a covalently adsorbed monolayer containing alkyl chains attached directly to gold, Hg(0) atoms, and no tosyl groups. It is stable against a variety of chemical agents. When the initial deposition is performed at a positive applied potential and is followed by oxidative electrochemical stripping, the mercury can be completely removed, leaving a gold surface covered only with alkyl chains. The details of the attachment structure are not known. The conclusions are based on infrared spectroscopy, X-ray and UV photoelectron spectroscopy, ellipsometry, contact angle goniometry, differential pulse polarography, and measurements of electrode blocking and electrochemical admittance.