Sec Form 4 Filing - Chambliss Kelly C @ CoreSite Realty Corp - 2021-12-28

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person Chambliss Kelly C 2. Issuer Name and Ticker or Trading Symbol CoreSite Realty Corp [ COR] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O CORESITE REALTY CORPORATION, 1001 17TH STREET, SUITE 500 3. Date of Earliest Transaction (MM/DD/YY) 12/28/2021 (Street) DENVER, CO80202 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Restricted Stock Units ( 1 ) 12/28/2021 D 8,896 ( 1 ) ( 1 ) Common Stock 8,896 ( 1 ) 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Chambliss Kelly C C/O CORESITE REALTY CORPORATION 1001 17TH STREET, SUITE 500 DENVER, CO80202 X Signatures /s/ Derek S. McCandless, Attorney-in-Fact 12/29/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )At the Company Merger Effective Time (as defined below), each award of restricted stock units ("Company Restricted Stock Unit Award") that was outstanding as of immediately prior to the Company Merger Effective Time vested in accordance with the terms of the applicable award agreement and all restrictions thereupon lapsed, and each such Company Restricted Stock Unit Award was converted into the right to receive a cash payment equal to the product of (i) the number of shares of shares of common stock, par value $0.01 per share, underlying such Restricted Stock Unit Award as of immediately prior to the Company Merger Effective Time and (ii) $170.00 in cash.

Remarks: This Form 4 reports securities disposed of under the terms of the Agreement and Plan of Merger (as amended or supplemented from time to time, the "Merger Agreement"), dated as of November 14, 2021, by and among the CoreSite Realty Corporation (the "Company"), CoreSite, L.P. ("Partnership"), Appleseed Merger Sub LLC ("Purchaser"), American Tower Investments LLC ("Parent"), Appleseed Holdco LLC ("Holdco"), Appleseed OP Merger Sub LLC ("OP Merger Sub") and, solely for the purposes of certain provisions specified therein, American Tower Corporation. Pursuant to the Merger Agreement, on December 28, 2021, (i) Purchaser merged with and into the Company, with the Company surviving as a wholly owned subsidiary of Holdco (the "Company Merger", and the effective time of such merger, the "Company Merger Effective Time"); (ii) substantially simultaneously with the Merger but preceding the Holdco Merger, OP Merger Sub merged with and into the Partnership, with the Partnership continuing as the surviving limited partnership (the "Partnership Merger"); and (iii) immediately following the Company Merger but after the Partnership Merger, the Company merged with and into Holdco, with Holdco continuing as the surviving limited liability company. A copy of the Merger Agreement is included as Exhibit 2.1 to the Company's Form 8-K filed with the SEC on November 14, 2021.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).

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