Construction and crystallization of expression system for RNA polymerase PB1-PB2 protein derived from influenza virus

A recombinant vector comprising a DNA encoding the polypeptide shown in (a1) or (a2) and a DNA encoding the polypeptide of (b1) or (b2) below:

• (a1) a PB1 polypeptide which consists of the amino acid sequence of SEQ ID NO:
• 2;
• or
• (a2) a PB1 polypeptide which consists of an amino acid sequence with at least 90% identity to the amino acid sequence of SEQ ID NO:
• 2 and which has binding activity to a fragment of influenza virus RNA polymerase PB2 subunit;
• and
• (b1) a PB2 polypeptide which consists of the amino acid sequence of SEQ ID NO:
• 4;
• or
• (b2) a PB2 polypeptide which consists of an amino acid sequence with at least 90% identity to the amino acid sequence of SEQ ID NO:
• 4 and which has binding activity to a fragment of influenza virus RNA polymerase PB1 subunit.

A cell transformed with a DNA encoding the polypeptide shown in (a1) or (a2) and a DNA encoding the polypeptide shown in (b1) or (b2) below:

• (a1) a PB1 polypeptide which consists of the amino acid sequence of SEQ ID NO:
• 2;
• or
• (a2) a PB1 polypeptide which consists of an amino acid sequence with at least 90% identity to the amino acid sequence of SEQ ID NO:
• 2 and which has binding activity to a fragment of influenza virus RNA polymerase PB2 subunit;
• and
• (b1) a PB2 polypeptide which consists of the amino acid sequence of SEQ ID NO:
• 4;
• or
• (b2) a PB2 polypeptide which consists of an amino acid sequence with at least 90% identity to the amino acid sequence of SEQ ID NO:
• 4 and which has binding activity to a fragment of influenza virus RNA polymerase PB1 subunit.

A method for screening a compound capable of serving as an active ingredient in anti-influenza drugs, which comprises the steps of:

• allowing a fragment of PB1 subunit and a fragment of PB2 subunit to contact each other in vitro in the presence of a candidate compound;
• and
• selecting a compound which inhibits the interaction between the fragment of PB1 subunit and the fragment of PB2 subunit, wherein the fragment of PB1 subunit consists of a polypeptide shown in (a1) or (a2) below, and the fragment of PB2 subunit consists of a polypeptide shown in (b1) or (b2) below:
• (a1) a PB1 polypeptide which consists of the amino acid sequence of SEQ ID NO:
• 2;
• or
• (a2) a PB1 polypeptide which consists of an amino acid sequence with at least 90% identity to the amino acid sequence of SEQ ID NO:
• 2 and which has binding activity to a fragment of influenza virus RNA polymerase PB2 subunit;
• and
• (b1) a PB2 polypeptide which consists of the amino acid sequence of SEQ ID NO:
• 4 or 20;
• or
• (b2) a PB2 polypeptide which consists of an amino acid sequence with at least 90% identity to the amino acid sequence of SEQ ID NO:
• 4 or 20 and which has binding activity to a fragment of influenza virus RNA polymerase PB1 subunit.