Total synthesis of a functional designer eukaryotic chromosome.

Rapid advances in DNA synthesis techniques have made it possible to engineer viruses, biochemical pathways and assemble bacterial genomes. Here, we report the synthesis of a functional 272,871-base pair designer eukaryotic chromosome, synIII, which is based on the 316,617-base pair native Saccharomyces cerevisiae chromosome III. Changes to synIII include TAG/TAA stop-codon replacements, deletion of subtelomeric regions, introns, transfer RNAs, transposons, and silent mating loci as well as insertion of loxPsym sites to enable genome scrambling.

The Build-a-Genome course.

Build-a-Genome is an intensive laboratory course at Johns Hopkins University that introduces undergraduates to the burgeoning field of synthetic biology. In addition to lectures that provide a comprehensive overview of the field, the course contains a unique laboratory component in which the students contribute to an actual, ongoing project to construct the first synthetic eukaryotic cell, a yeast cell composed of man-made parts. In doing so, the students acquire basic molecular biology skills and gain a truly "graduate student-like experience" in which they take ownership of their projects, troubleshoot their own experiments, present at frequent laboratory meetings, and are given 24-h access to the laboratory, albeit with all the guidance they will need to complete their projects during the semester.

Assembling large DNA segments in yeast.

As described in a different chapter in this volume, the uracil-specific excision reaction (USER) fusion method can be used to assemble multiple small DNA fragments (∼0.75-kb size) into larger 3-kb DNA segments both in vitro and in vivo (in Escherichia coli). However, in order to assemble an entire synthetic yeast genome (Sc2.

Assembling DNA fragments by USER fusion.

Recent advances in DNA synthesis technology make it possible to design and synthesize DNA fragments of several kb in size. However, the process of assembling the smaller DNA fragments into a larger DNA segment is still a cumbersome process. In this chapter, we describe the use of the uracil specific excision reaction (USER)-mediated approach for rapid and efficient assembly of multiple DNA fragments both in vitro and in vivo (using Escherichia coli).

Polyubiquitin-sensor proteins reveal localization and linkage-type dependence of cellular ubiquitin signaling.

Polyubiquitin chain topology is thought to direct modified substrates to specific fates, but this function-topology relationship is poorly understood, as are the dynamics and subcellular locations of specific polyubiquitin signals. Experimental access to these questions has been limited because linkage-specific inhibitors and in vivo sensors have been unavailable. Here we present a general strategy to track linkage-specific polyubiquitin signals in yeast and mammalian cells, and to probe their functions.

Specificity of the BRISC deubiquitinating enzyme is not due to selective binding to Lys63-linked polyubiquitin.

BRISC (Brcc36-containing isopeptidase complex) is a four-subunit deubiquitinating (DUB) enzyme that has a catalytic subunit, called Brcc36, that is a member of the JAMM/MPN(+) family of zinc metalloproteases. A notable feature of BRISC is its high specificity for cleaving Lys(63)-linked polyubiquitin. Here, we show that BRISC selectivity is not due to preferential binding to Lys(63)-linked polyubiquitin but is instead dictated by how the substrate isopeptide linkage is oriented within the enzyme active site.

K63-specific deubiquitination by two JAMM/MPN+ complexes: BRISC-associated Brcc36 and proteasomal Poh1.

An unusual deubiquitinating (DUB) activity exists in HeLa cell extracts that is highly specific for cleaving K63-linked but not K48-linked polyubiquitin chains. The activity is insensitive to both N-ethyl-maleimide and ubiquitin aldehyde, indicating that it lacks an active site cysteine residue, and gel filtration experiments show that it resides in a high molecular weight (approximately 600 kDa) complex. Using a biochemical approach, we found that the K63-specific DUB activity co-fractionated through seven chromatographic steps with three multisubunit complexes: the 19S (PA700) portion of the 26S proteasome, the COP9 signalosome (CSN) and a novel complex that includes the JAMM/MPN+ domain-containing protein Brcc36.

Evidence for bidentate substrate binding as the basis for the K48 linkage specificity of otubain 1.

Otubain 1 belongs to the ovarian tumor (OTU) domain class of cysteine protease deubiquitinating enzymes. We show here that human otubain 1 (hOtu1) is highly linkage-specific, cleaving Lys48 (K48)-linked polyubiquitin but not K63-, K29-, K6-, or K11-linked polyubiquitin, or linear alpha-linked polyubiquitin. Cleavage is not limited to either end of a polyubiquitin chain, and both free and substrate-linked polyubiquitin are disassembled.

Biochemical analysis of Angelman syndrome-associated mutations in the E3 ubiquitin ligase E6-associated protein.

Angelman syndrome is a severe neurological disorder characterized by mental retardation, absent speech, ataxia, seizures, and hyperactivity. The gene affected in this disorder is UBE3A, the gene encoding the E6-associated protein (E6AP) ubiquitin-protein ligase. Most patients have chromosomal deletions that remove the entire maternal allele of UBE3A.