Yeast artificial chromosomes

Yeast artificial chromosomes (YACs) are synthetic double stranded linear constructs containing the elements necessary for replication as independent chromosomes in yeast. These elements are:
 * an autonomous replication sequence (ARS): ARS1, chromosome III ARS, ARSH4
 * a centromere: CEN4, CEN6: centromeres consist of three centromere determining elements, CDE I, CDE II, and CDE III.
 * a telomeric sequence at each end

Typically the chromosome also contains a selection marker such as TRP1, Lys2 or Ura3.

Minimal size for a YAC is between 50kb and 100kb, while maximum sizes are 1Mb to 3Mb.

A common tool for constructing YACs is a shuttle plasmid such as pYAC4 which replicates in E. coli, has a multiple cloning site, and a pair of telomeres which can be cleaved to form a linear fragment. Available as an E.coli plasmid ATCC 67379, sequence at U01086.

There are two common centromere sequences, CEN4 and CEN6. CEN4 is found in most yeast centromere-containiing vectors, such as pYAC4. These vectors typically use ARS1 sequences.

The pRS313- pRS316 plasmids use the CEN6 + ARSH4 cassette (Sikorski89).

Yeast strains

 * AB1380 (MATa ura3-52 trp1 lys2-1 ade2-1 can1-100 his5) (Burke87) ATCC 204682
 * J57D (MATa, ura3-52, trp1 ade2-101 can1-100 leu2-3, 112 his3-6) (Haldi96)
 * claimed to be 2-3x more efficient at large insert cloning than AB1380
 * W303-1a (MATa leu2-3,112 trp1-1 can1-100 ura3-1 ade2-1 his3-11,15 ybp1-1) Rothstein notes (see Veal03) Open Biosystems: YSC1058
 * YPH500 (MAT&alpha; ura3-52 lys2-801_amber ade2-101_ochre trp1-&Delta;63 his1-&Delta;200 leu2-&Delta;1) ATCC:204680 (Sikorski89)
 * S288C (MAT&alpha; SUC2 gal2 mal mel flo1 flo8-1 hap1) ATCC: 204508 (Mortimer86)

YAC Plasmids

 * pYAC4 (Burke87) has Sup4 for ade2 selection, interrupted by the cloning site (EcoRI), ura3, a pair of facing telomeres surrounding a his3 gene (linearized and cut out with BamHI), a pBR322 based E. coli replication and ampR region, a barely functional TRP1 gene, ARS1 and  CEN4.  Sequence at Genbank U01086


 * pJS97 / pJS98 plasmids (Shero91) are available at ATCC 77191 as a two-plasmid kit.  Each plasmid supplies one chromosome end.
 * pJS97 has CEN4 and ARSH4, URA3 gene, Sup11 tRNA for ade2 selection,  a pUC19 derived E. coli replication region, including ampR,  and a telomere.
 * pJS98 has ARSH4, a functional TRP1 gene, a pUC19 derived E. coli replication region including ampR, and a telomere.


 * pCGS966 (Smith90, Smith92, Moir93) has ARS1 on both arms, Gal inducible extra copy production, NeoR for mammalian expression and a functional promoter for the Trp gene, unlike pYAC4.


 * pRML1 / pRML2 (Spencer93) are similar to pJS97/8 (Haldi96)
 * see sequence information here
 * see [[media: pat5776745.pdf | US Patent 5776745, Ketner et al. 1998]]
 * pRML1 vector NTI genbank format file: [[media:PRML1.gb | here]]
 * pRML2 vector NTI genbank format file: [[media:PRML2.gb | here]]
 * Knight:pRML1/2-sequencing