(ShareCast News) - Specialist trade publisher and events company UBM reached milestone in its sale of PR Newswire on Monday, with confirmation that the US Department of Justice has filed its proposed settlement under the Hart-Scott-Rodino Antitrust Improvements Act.The FTSE 250 firm initially announced the sale of the newswire service to PWW Acquisition - a Cision entity controlled by GTCR Canyon Holdings - after much speculation on 15 December last year.Under the Hart-Scott-Rodino Act, mergers, acquisitions and transfers cannot be completed until the Federal Trade Commission and Department of Justice have filed their approval under antitrust laws.The transaction is now subject to a mandatory waiting period, although "UBM expects the government to grant early termination of the Hart-Scott-Rodino Act waiting period shortly, which would then permit the parties to close the transaction," its board said in a statement.