(1) Imposition of tax There is hereby imposed for each taxable year on the unrelated business taxable income of every trust described in paragraph (2) a tax computed as provided in section
1 (e). In making such computation for purposes of this section, the term taxable income as used in section
1 shall be read as unrelated business taxable income as defined in section
512.
(2) Charitable, etc., trusts subject to tax The tax imposed by paragraph (1) shall apply in the case of any trust which is exempt, except as provided in this part or part II (relating to private foundations), from taxation under this subtitle by reason of section
501 (a) and which, if it were not for such exemption, would be subject to subchapter J (sec.
641 and following, relating to estates, trusts, beneficiaries, and decedents).