IRC Sec. 362 in the case of a corporation. IRC Sec. 723 in the case of a partnership. Reg. Sec. 1.1001-1(a). IRC Sec. 351(b).
Reg. Sec. 1.707-3(f), Ex. 1. IRC Sec. 1012. IRC Sec. 723. The HC would then drop down the contributed interest to its subsidiary, following which the subsidiary will own all of the equity in the target partnership, and the target will become a disregarded entity for tax purposes.