Ownership Submission
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 OF SECURITIES

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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(Print or Type Responses)
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. NW, SUITE 220S
3. Date of Earliest Transaction (Month/Day/Year)
05/01/2015
(Street)

WASHINGTON, DC 20004
4. If Amendment, Date Original Filed(Month/Day/Year)
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 (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 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 05/01/2015   M   4,500,000 A (1) 4,500,000 I See footnotes (2) (3) (4)
Common Stock 05/01/2015   S   4,500,000 D $ 48.67 0 I See footnotes (2) (3) (4)

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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 (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 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
(Month/Day/Year)
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) 05/01/2015   M     4,500,000   (1)   (1) Common Stock 4,500,000 (1) 20,775,390 I See footnotes (2) (3) (4)

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. NW, SUITE 220S
WASHINGTON, DC 20004
    X    
Carlyle Realty III, L.P.
C/O THE CARLYLE GROUP
1001 PENNSYLVANIA AVE. NW, SUITE 220S
WASHINGTON, DC 20004
    X    
CoreSite CRP III Holdings, LLC
C/O THE CARLYLE GROUP
1001 PENNSYLVANIA AVE. NW, SUITE 220S
WASHINGTON, DC 20004
    X    
CRP III AIV GP, L.L.C.
C/O THE CARLYLE GROUP
1001 PENNSYLVANIA AVE. NW, SUITE 220S
WASHINGTON, DC 20004
    X    
CRP III AIV GP, L.P.
C/O THE CARLYLE GROUP
1001 PENNSYLVANIA AVE. NW, SUITE 220S
WASHINGTON, DC 20004
    X    
CRQP III AIV, L.P.
C/O THE CARLYLE GROUP
1001 PENNSYLVANIA AVE. NW, SUITE 220S
WASHINGTON, DC 20004
    X    
CoreSite CRP III Holdings (VCOC), LLC
C/O THE CARLYLE GROUP
1001 PENNSYLVANIA AVE. NW, SUITE 220S
WASHINGTON, DC 20004
    X    
Carlyle Realty IV GP, L.L.C.
C/O THE CARLYLE GROUP
1001 PENNSYLVANIA AVE. NW, SUITE 220S
WASHINGTON, DC 20004
    X    
Carlyle Realty IV, L.P.
C/O THE CARLYLE GROUP
1001 PENNSYLVANIA AVE. NW, SUITE 220S
WASHINGTON, DC 20004
    X    
CoreSite CRP IV Holdings, LLC
C/O THE CARLYLE GROUP
1001 PENNSYLVANIA AVE. NW, SUITE 220S
WASHINGTON, DC 20004
    X    

Signatures

 /s/ R. Rainey Hoffman, attorney-in-fact for Daniel A. D'Aniello, Chairman   05/05/2015
**Signature of Reporting Person Date

Explanation of Responses:

* 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).
(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) 5,114,769 common units held by CoreSite CRP III Holdings, LLC; (ii) 1,036,123 common units held by CoreSite CRP III Holdings (VCOC), LLC; (iii) 3,584,431 common units held by CoreSite CRP IV Holdings, LLC; (iv) 610,419 common units held by CoreSite CRP IV Holdings (VCOC I), LLC; (v) 1,568,923 common units held by CoreSite CRP IV Holdings (VCOC II), LLC; and (vi) 8,860,725 common units held by CoreSite CRP V Holdings, LLC.
(3) Carlyle Group Management L.L.C. is the general partner of The Carlyle Group L.P., which is a publicly traded entity listed on NASDAQ. The Carlyle Group L.P. 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 is the managing member of TC Group, L.L.C., which is the general partner of TC Group Sub L.P., which is the managing 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.
(4) 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 is the general partner of CRQP III AIV, L.P., which is the managing 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 L.P., Carlyle Holdings I GP Inc., Carlyle Holdings I GP Sub L.L.C., Carlyle Holdings I L.P., 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.

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