Stimulation of yeast telomerase activity by the ever shorter telomere 3 (Est3) subunit is dependent on direct interaction with the catalytic protein Est2.

Telomerase is a multisubunit enzyme that maintains genome stability through its role in telomere replication. Although the Est3 protein is long recognized as an essential telomerase component, how it associates with and functions in the telomerase complex has remained enigmatic. Here we provide the first evidence of a direct interaction between Saccharomyces cerevisiae Est3p and the catalytic protein subunit (Est2p) by demonstrating that recombinant Est3p binds the purified telomerase essential N-terminal (TEN) domain of Est2p in vitro.

Structural bases of dimerization of yeast telomere protein Cdc13 and its interaction with the catalytic subunit of DNA polymerase α.

Budding yeast Cdc13-Stn1-Ten1 (CST) complex plays an essential role in telomere protection and maintenance, and has been proposed to be a telomere-specific replication protein A (RPA)-like complex. Previous genetic and structural studies revealed a close resemblance between Stn1-Ten1 and RPA32-RPA14. However, the relationship between Cdc13 and RPA70, the largest subunit of RPA, has remained unclear.

Is there a telomere-bound 'EST' telomerase holoenzyme?

Eukaryotic linear chromosomes culminate in nucleoprotein structures designated telomeres. The terminal telomeric DNA consists of tandem repeats of a G-rich motif that is established and maintained by the action of the specialized reverse transcriptase telomerase. In addition to the core enzyme, effective replication of telomeric DNA requires a number of regulatory factors.

HSP90 manages the ends.

The telomere environment requires an efficient means to assemble and disassemble a multitude of structures to operate correctly and to help achieve cellular homeostasis. Telomeres are challenged by a common binding specificity displayed by many of the protein components for telomeric DNA, which could result in competitive DNA interactions, and by a cell cycle-restricted timing of events, which enforces a narrow working period in which to perform numerous tasks. In this review, we discuss how the HSP90 molecular chaperone network avoids these obstacles and facilitates an effective operation of the telomere system.

Slowing bacterial translation speed enhances eukaryotic protein folding efficiency.

The mechanisms for de novo protein folding differ significantly between bacteria and eukaryotes, as evidenced by the often observed poor yields of native eukaryotic proteins upon recombinant production in bacterial systems. Polypeptide synthesis rates are faster in bacteria than in eukaryotes, but the effects of general variations in translation rates on protein folding efficiency have remained largely unexplored. By employing Escherichia coli cells with mutant ribosomes whose translation speed can be modulated, we show here that reducing polypeptide elongation rates leads to enhanced folding of diverse proteins of eukaryotic origin.

The conserved Est1 protein stimulates telomerase DNA extension activity.

The first telomerase cofactor identified was the budding yeast protein Est1, which is conserved through humans. While it is evident that Est1 is required for telomere DNA maintenance, understanding its mechanistic contributions to telomerase regulation has been limited. In vitro, the primary effect of Est1 is to activate telomerase-mediated DNA extension.

The Hsp82 molecular chaperone promotes a switch between unextendable and extendable telomere states.

Distinct protein assemblies are nucleated at telomeric DNA to both guard the ends from damage and lengthen the DNA after replication. In yeast, Cdc13 recruits either Stn1-Ten1 to form a protective cap or the telomerase holoenzyme to extend the DNA. We have established an in vitro yeast telomere system in which Stn1-Ten1-unextendable or telomerase-extendable states can be observed.

HSP90: the Rosetta stone for cellular protein dynamics?

The Hsp90 proteomic network is expansive and includes a variety of cell processes operating within the cytoplasm and nucleoplasm. Though the functional significance of the extensive interactions has not been defined, we suggest that the Hsp90 molecular chaperone machinery promotes dynamic behaviors for client proteins that is critical to achieve homeostasis. A general rapid action by cell factors would permit both proper assembly of biological complexes and efficient transitions between distinct structures.

The hsp90 molecular chaperone modulates multiple telomerase activities.

The Hsp90 molecular chaperone is a highly abundant eukaryotic molecular chaperone. While it is understood that Hsp90 modulates a significant number of proteins, the mechanistic contributions made by Hsp90 to a client protein typically are not well understood. Here we investigate the yeast Hsp90 regulatory roles with telomerase.

Purification and characterization of enterocin 62-6, a two-peptide bacteriocin produced by a vaginal strain of Enterococcus faecium: Potential significance in bacterial vaginosis.

A bacteriocin produced by a vaginal isolate of Enterococcus faecium strain 62-6, designated enterocin 62-6, was characterized following purification and DNA sequence analysis and compared to previously described bacteriocins. Enterocin 62-6 was isolated from brain heart infusion (BHI) culture supernatants using ammonium sulfate precipitation followed by elution from a Sepharose cation exchange column using a continuous salt gradient (0.1-0.