While you don't own the original building and land, you DO own the improvements that you made.
I'll point you to the actual law itself - Regulation §1.167(a)-4:
§ 1.167(a)-4 Leased property.
(a) In general. Capital expenditures made by either a lessee or lessor for the erection of a building or for other permanent improvements on leased property are recovered by the lessee or lessor under the provisions of the Internal Revenue Code (Code) applicable to the cost recovery of the building or improvements, if subject to depreciation or amortization, without regard to the period of the lease. For example, if the building or improvement is property to which section 168 applies, the lessee or lessor determines the depreciation deduction for the building or improvement under section 168.
https://www.law.cornell.edu/cfr/text/26/1.167(a)-4
