FEBRUARY 15-16 - MINUTES OF MEETING 
12 
During the 30-day period for comment, no comments were received. Prior 
to consideration of this proposal, the RAC had recommended the criteria 
for S. cerevisiae as an HV2 system described in IV-B above. 
The application had been reviewed by the Lower Eukaryotic Host-Vector 
Working Group and recommended to the RAC for acceptance. The basis of 
containment in the HV2 systems is the inability of cloned DNA in a sterile 
yeast host to be transferred out of the host to other laboratory or wild 
type strains. The level of containment achieved by the HV2 system is 
acceptable based primarily upon the sterility, the probability of encounter- 
ing an appropriate haploid strain in nature which is capable of mating, 
and the inefficiency of mating in dilute suspension. 
The following sterile strains of yeast, all of which have the ste- VC9 
mutation, were proposed as HV2 hosts: SHY1, SHY2, SHY3 and SHY4. 
The preposed HV2 plasmid vectors have in common several characteristics. 
They all contain a bacterial replicon derived from the certified EK2 
vector, pBR322, which makes possible the amplification of the DNA in 
E. coli. Another common characteristic is the presence of markers which 
enable selection in EL coli for the presence of the plasmid. Seme of 
these markers are drug-resistance genes derived from pBR322. Others, 
however, are yeast DNA fragments which are expressed in EL coli K-12: 
these include the ura3 r leu2, his3, and trpl genes. 
Most of the vectors also carry one or more genes of yeast origin which 
can be used to select the presence of the vector in yeast, such as ura3, 
leu 2, trpl , and his3. The SHY strains are arranged to make any or all 
of these genes selectable. All the vectors also carry fragments of 
yeast DNA which provide for the maintenance of the plasmid in yeast. 
The following are the proposed HV2 plasmid vectors: YIpl YEp2, YEp4, 
YIp5, YEp6 , YRp7, YEp20, YEp21, YEp24, YIp25, YIp26, YIp27, YIp28, YIp29, 
YIp30 , YIp31, YIp32, YIp33. 
Drs. Davis and Botstein were present to answer technical questions regard- 
ing the proposed hosts and vectors. It was noted that the vectors must 
be approvable as components in an EK2 system using xl776 as a host for 
the systems to be useful. Dr. Novick felt that the containment of pBR322 
will not be comprised in the proposed system. 
The RAC voted 17 to 0 with 3 abstentions to recommend certification of 
the proposed systems because they are considered to meet adequately the 
criteria for HV2 £5. cerevisiae systems. Drs. Baltimore and Campbell 
abstained from the vote. 
[ 58 ] 
