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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1. Name and Address of Reporting Person * MARCATO CAPITAL MANAGEMENT LLC   2. Issuer Name and Ticker or Trading Symbol CyrusOne Inc. [CONE] 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) ONE MONTGOMERY STREET, SUITE 3250 3. Date of Earliest Transaction (Month/Day/Year) 06/26/2013 (Street) SAN FRANCISCO, CA 94104 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, $0.01 par value per share 06/26/2013   S   383,000 D $ 18.97 (1) 2,209,394 I See Footnote (2)

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

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
MARCATO CAPITAL MANAGEMENT LLC ONE MONTGOMERY STREET SUITE 3250 SAN FRANCISCO, CA 94104		X
McGuire Richard ONE MONTGOMERY STREET SUITE 3250 SAN FRANCISCO, CA 94104		X
Marcato International Master Fund, Ltd. C/O OGIER FIDUCIARY SERVICES (CAYMAN)LTD 89 NEXUS WAY, CAMANA BAY GRAND CAYMAN, E9 KY1-9007		X
Marcato, L.P. ONE MONTGOMERY STREET SUITE 3250 SAN FRANCISCO, CA 94104		X
Marcato II, L.P. ONE MONTGOMERY STREET SUITE 3250 SAN FRANCISCO, CA 94104		X

Signatures

Marcato Capital Management LLC; By: /s/ Richard McGuire III, Managing Member		06/26/2013
**Signature of Reporting Person		Date
/s/ Richard McGuire III		06/26/2013
**Signature of Reporting Person		Date
Marcato International Master Fund, Ltd., By: /s/ Richard McGuire III, Director		06/26/2013
**Signature of Reporting Person		Date
Marcato, L.P., By: /s/ Richard McGuire III, Director		06/26/2013
**Signature of Reporting Person		Date
Marcato II, L.P., By: /s/ Richard McGuire III, Director		06/26/2013
**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 price shown in Column 4 is a weighted average sale price. The price range for the sales is $18.95 to $19.10. The Reporting Person undertakes to provide upon request by the staff of the Securities and Exchange Commission, the issuer or a security holder of the issuer, full information regarding the number of shares sold at each separate price.
(2)	The securities are held in the accounts of Marcato International Master Fund, Ltd., Marcato, L.P. and Marcato II, L.P. (collectively, the "Funds") and may be deemed to be beneficially owned by (i) Marcato Capital Management LLC, the investment manager or general partner, as applicable, of the Funds, and (ii) Richard McGuire III, the managing member of Marcato Capital Management LLC. Each of Marcato Capital Management LLC and Richard McGuire III disclaims beneficial ownership of these reported securities except to the extent of its pecuniary interest therein, and this report shall not be deemed an admission that any such person is the beneficial owner of these securities for purposes of Section 16 of the U.S. Securities Exchange Act of 1934, as amended, or for any other purpose.

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