For most purposes, cloning protocols based on the polymerase chain reaction (PCR) using either the template-independent terminal transferase activity of Taq DNA polymerase in TA cloning schemes (8,9) or blunt-endbased procedures involving Pwo or Pfu DNA polymerase or polished Taq-generated PCR products are quite satisfactory. Nevertheless, both techniques have been proven less straightforward t...

We have studied the resistance of cytosine methylated DNA to digestion by the restriction endonuclease HinfI, using a simple PCR procedure to synthesize DNA of known sequence in which every cytosine is methylated at the 5 position. We find that HinfI cannot digest cytosine methylated DNA at the concentrations normally used in restriction digests. Complete digestion is possible using a vast exce...

DNA polymerases amplify DNA fragments through primer extension reactions. However, polymerization behavior of short primers in the primer extension process has not been systematically explored. In this study, we examined the minimal primer length required for primer extension, and the effect of primer length, mismatches and other conditions on DNA polymerization using a non-radioactive method. ...

Phage fd RF I DNA1 about 90% substituted by deoxy-4-thiothymidine (s4Td) in the codogenic strand was synthesized by the simultaneous actions of DNA polymerase I and DNA ligase. While the rate of DNA synthesis was considerably reduced, the yield the rate of DNA synthesis was considerably reduced, the yield was not affected in the presence of s4TdTP. The conversion of RF II to RF I DNA by DNA lig...

We discovered a thermostable enzyme from the archaeon Pyrococcus furiosus (Pfu), which increases yields of PCR product amplified with Pfu DNA polymerase. A high molecular mass (>250 kDa) complex with PCR-enhancing activity was purified from Pfu extracts. The complex is a multimer of two discrete proteins, P45 and P50, with significant similarity to bacterial dCTP deaminase/dUTPase and DNA flavo...

Two restriction-modification systems have been previously discovered in Thermus aquaticus YT-1. TaqI is a 263-amino acid (aa) Type IIP restriction enzyme that recognizes and cleaves within the symmetric sequence 5'-TCGA-3'. TaqII, in contrast, is a 1105-aa Type IIC restriction-and-modification enzyme, one of a family of Thermus homologs. TaqII was originally reported to recognize two different ...

A highly efficient cloning vector was constructed for cloning PCR products by inserting an 80 bp DNA fragment into pGEM-5zf (+) vector. The Xcm I digestion of this vector gave rise to a 3' overhanging deoxythymidine offering the possibility of cloning PCR products with 3' adenosine overhang created by Taq DNA polymerase. Furthermore, two EcoR I sites were added to the construct for identificati...

Polymerase chain reaction (PCR) methodology (1) has become a routine method for selectively amplifying segments of DNA from a wide variety of sources. Amplification of specific sequences is dependent upon an exact match between the template DNA and the oligonucleotide primers. Mismatches at the 3' terminus lead to greatly reduced amplification, with no detectable product when amplified under th...