Sec Form 4 Filing - Carlyle Realty III, GP, L.L.C. @ CoreSite Realty Corp - 2020-05-07

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 Carlyle Realty III, GP, L.L.C. 2. Issuer Name and Ticker or Trading Symbol CoreSite Realty Corp [ COR] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O THE CARLYLE GROUP, 1001, PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH 3. Date of Earliest Transaction (MM/DD/YY) 05/07/2020 (Street) WASHINGTON, DC20004 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ 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 Common Stock 05/07/2020 M 2,620,000 A 2,620,000 I See footnotes ( 2 ) ( 3 ) ( 4 ) ( 5 ) Common Stock 05/07/2020 S 2,620,000 D $ 118.4607 0 I See footnotes ( 2 ) ( 3 ) ( 4 ) ( 5 )

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 Operating Partnership Units ( 1 ) 05/07/2020 M 2,620,000 ( 1 ) ( 1 ) Common Stock 2,620,000 ( 1 ) 8,105,390 I See footnotes ( 2 ) ( 3 ) ( 4 ) ( 5 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Carlyle Realty III, GP, L.L.C. C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH WASHINGTON, DC20004 X Carlyle Realty III, L.P. C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH WASHINGTON, DC20004 X CoreSite CRP III Holdings, LLC C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH WASHINGTON, DC20004 X CRP III AIV GP, L.L.C. C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH WASHINGTON, DC20004 X CRP III AIV GP, L.P. C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH WASHINGTON, DC20004 X CRQP III AIV, L.P. C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH WASHINGTON, DC20004 X CoreSite CRP III Holdings (VCOC), LLC C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH WASHINGTON, DC20004 X Carlyle Realty IV GP, L.L.C. C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH WASHINGTON, DC20004 X Carlyle Realty IV, L.P. C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH WASHINGTON, DC20004 X CoreSite CRP IV Holdings, LLC C/O THE CARLYLE GROUP, 1001 PENNSYLVANIA AVE., N.W. SUITE 220 SOUTH WASHINGTON, DC20004 X Signatures Carlyle Realty III, GP, L.L.C.By: /s/ Kevin Gasque, Authorized Person 05/11/2020 Signature of Reporting Person Date Carlyle Realty III, L.P.By: /s/ Kevin Gasque, Authorized Person 05/11/2020 Signature of Reporting Person Date CoreSite CRP III Holdings, LLCBy: Carlyle Realty III, L.P., its managing memberBy: /s/ Kevin Gasque, Authorized Person 05/11/2020 Signature of Reporting Person Date CRP III AIV GP, L.L.C.By: /s/ Kevin Gasque, Authorized Person 05/11/2020 Signature of Reporting Person Date CRP III AIV GP, L.P.By: /s/ Kevin Gasque, Authorized Person 05/11/2020 Signature of Reporting Person Date CRQP III AIV, L.P.By: CRP III AIV GP, L.P., its general partnerBy: /s/ Kevin Gasque,Authorized Person 05/11/2020 Signature of Reporting Person Date CoreSite CRP III Holdings (VCOC), LLCBy: CRQP III AIV, L.P., its managing memberBy: CRP III AIV GP, L.P., its general partnerBy: /s/ Kevin Gasque,Authorized Person 05/11/2020 Signature of Reporting Person Date Carlyle Realty IV GP, L.L.C.By: /s/ Kevin Gasque, Authorized Person 05/11/2020 Signature of Reporting Person Date Carlyle Realty IV, L.P.By: /s/ Kevin Gasque, Authorized Person 05/11/2020 Signature of Reporting Person Date CoreSite CRP IV Holdings, LLCBy: Carlyle Realty IV, L.P., its managing memberBy: /s/ Kevin Gasque, Authorized Person 05/11/2020 Signature of Reporting Person Date

Explanation of Responses:

( 1 )The operating partnership units are redeemable at any time for cash or, at the election of the Issuer, exchangeable for shares of common stock on a one-for-one basis, and have no expiration date. ( 2 )Following the transactions reported herein, consists of (i) 957,374 common units held by CoreSite CRP III Holdings, LLC; (ii) 193,940 common units held by CoreSite CRP III Holdings (VCOC), LLC; (iii) 670,930 common units held by CoreSite CRP IV Holdings, LLC; (iv) 114,259 common units held by CoreSite CRP IV Holdings (VCOC I), LLC; (v) 293,669 common units held by CoreSite CRP IV Holdings (VCOC II), LLC; and (vi) 5,875,218 common units held by CoreSite CRP V Holdings, LLC. ( 3 )Following an internal reorganization and by reason of the relationships described below, the reporting person may be deemed to share beneficial ownership of the securities reported herein. The reporting person disclaims beneficial ownership of any such securities, except to the extent of its pecuniary interest therein. ( 4 )Carlyle Group Management L.L.C. holds an irrevocable proxy to vote a majority of the shares of The Carlyle Group Inc., which is a publicly traded entity listed on NASDAQ. The Carlyle Group Inc. is the sole shareholder of Carlyle Holdings I GP Inc., which is the managing member of Carlyle Holdings I GP Sub L.L.C., which is the general partner of Carlyle Holdings I L.P., which, with respect to the securities reported herein, is the managing member of CG Subsidiary Holdings L.L.C., which is the sole member of TC Group, L.L.C., which is the general partner of TC Group Sub L.P., which is the sole member of each of Carlyle Realty III GP, L.L.C., CRP III AIV GP, L.L.C., Carlyle Realty IV GP, L.L.C., CRP IV AIV GP, L.L.C. and Carlyle Realty V GP, L.L.C. ( 5 )Carlyle Realty III GP, L.L.C. is the general partner of Carlyle Realty III, L.P. which is the manager of CoreSite CRP III Holdings, LLC. CRP III AIV GP, L.L.C. is the general partner of CRP III AIV GP, L.P., which i s the general partner of CRQP III AIV, L.P., which is the sole member of CoreSite CRP III Holdings (VCOC), LLC. Carlyle Realty IV GP, L.L.C. is the general partner of Carlyle Realty IV, L.P., which is the manager of CoreSite CRP IV Holdings, LLC. CRP IV AIV GP, L.L.C. is the general partner of CRP IV AIV GP, L.P., which is the general partner of each of CRP IV-A AIV, L.P. and CRQP IV AIV, L.P., which are the managing members of CoreSite CRP IV Holdings (VCOC I), LLC and CoreSite CRP IV Holdings (VCOC II), LLC, respectively. Carlyle Realty V GP, L.L.C. is the general partner of Carlyle Realty V, L.P., which is the manager of CoreSite CRP V Holdings, LLC.

Remarks: Due to the limitations of the electronic filing system Carlyle Group Management L.L.C., The Carlyle Group Inc., Carlyle Holdings I GP Inc., Carlyle Holdings I GP Sub L.L.C., Carlyle Holdings I L.P., CG Subsidiary Holdings L.L.C., TC Group, L.L.C., TC Group Sub L.P., CRP IV AIV GP, L.L.C., CRP IV AIV GP, L.P., CRP IV-A AIV, L.P., CRQP IV AIV, L.P., CoreSite CRP IV Holdings (VCOC I), LLC, CoreSite CRP IV Holdings (VCOC II), LLC, Carlyle Realty V GP, L.L.C., Carlyle Realty V, L.P. and CoreSite CRP V Holdings, LLC are filing a separate Form 4.

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).

** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

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