Archease as rna ligase complex member

A kit suitable for enhancing polynucleotide ligation or for determining Archease activity, comprising an Archease molecule, a RNA ligase reaction buffer comprising buffer components and one or more metal ions selected from Mg2+, Mn2+, Ni2+ or mixtures thereof, for use in a final concentration range of ca 0.1-20 mM, preferably 1-10 mM, in particular preferred 2-5 mM, optionally further comprising a RNA molecule with 2′,3′-cyclic phosphate, preferably further with a label, preferably said kit further comprising a RNA ligase enzyme;

• or comprising an Archease molecule and GTP, preferably further with a label, preferably said kit further comprising a RNA ligase enzyme.

A transgenic cell comprising an exogenously expressed Archease protein, preferably with an inducible promoter, and an exogenously expressed RNA ligase enzyme, preferably with an inducible promoter.

An Archease knock-out cell or cell with reduced or inhibited endogenous Archease expression, preferably further with reduced or inhibited RNA ligase expression, preferably HSPC117 expression.

A method of reducing RNA ligase activity in a cell comprising inhibiting an Archease in the cell, preferably by knock-out or RNAi.

The method of preventing apoptosis in a cell due to unfolded protein accumulation, said method comprising increasing Archease protein amounts or expression levels in said cell, whereby an unfolded protein response in said cell is increased.

A method of reducing tumor cell growth or in the treatment of a disease or infection dependent on host polymerases, such as hepatitis delta virus infection, or XBP1, such as T cell leukemia virus or Kaposi's sarcoma-associated herpesvirus or Epstein Barr virus, comprising administering an Archease inhibitor to said cell, preferably in combination with a RNA ligase inhibitor;

• or of treating a disease in a subject associated with dysfunctional tRNA splicing, preferably pontocerebellar hypoplasia, or with a dysfunctional UPR, such as diabetes type II, comprising administering a Archease molecule to said subject, preferably in combination with a RNA ligase.

A method of obtaining an Archease or a combined Archease-RNA ligase inhibitor, comprising a) contacting Archease with a candidate inhibitor or b) contacting a combination of Archease and a RNA ligase, preferably HSPC117, with a candidate inhibitor, and

• i) determining the activity of a RNA ligase in contact with said Archease or of the combined Archease-RNA ligase, wherein an inhibitor is obtained when said activity of said RNA ligase is reduced in comparison to said method without contacting with said inhibitor;
• or
• ii) determining guanylation of the RNA ligase by the Archease, wherein an inhibitor is obtained when guanylation activity of the Archease is reduced in comparison to said method without contacting with said inhibitor.