* Reform hopes on Shiozaki helps stock market sentiment - traders * Strong department store sales supports retail stocks By Ayai Tomisawa TOKYO, Sept 2 (Reuters) - Japan's Nikkei share average rose to a 4-1/2-week high on Tuesday morning as the yen slipped to a seven-month low against the dollar, sending exporters higher on hopes of a boost to earnings.

The Nikkei gained 1.1 percent to 15,639.72 in mid-morning trade, the highest level since July 31.

A planned cabinet reshuffle by Prime Minister Shinzo Abe also supported sentiment, traders said.

The Nikkei business daily reported that Abe has decided to bring Yasuhisa Shiozaki, a veteran Liberal Democratic Party (LDP) and vocal proponent of overhauling Japan's Government Pension Investment Fund, for the labor and welfare minister post.

"Shiozaki is seen taking an important role for Abe's growth strategy," said Nobuhiko Kuramochi, a strategist at Mizuho Securities. "If he speeds up the pension fund's reform plan, it would be good for the stock market." GPIF is finalising plans to boost the weighting of domestic stocks in its portfolio to more than 20 percent from a current 12 percent target, people involved in the review told Reuters last month.

On Tuesday, exporters benefited from the weaker yen, with dollar rising to a high of 104.64, its strongest mark since mid-January.

Toyota Motor Corp rose 1.1 percent, Toshiba Corp added 1.4 percent and Fanuc Corp advanced 1.9 percent.

A weak yen sharpens Japanese exporters' competitiveness abroad and lifts their profits when repatriated.

Department store operators also gained after their monthly sales in August rose for the first time since the sales tax was raised to 8 percent from 5 percent in April. Takashimaya Co rose 1.0 percent, Isetan Mitsukoshi Holdings jumped 1.8 percent and J.Front Retailing Co soared 3.1 percent.

The broader Topix rose 0.9 percent to 1,294.52, and the JPX-Nikkei Index 400 gained 1.0 percent to 11,749.88.

(Editing by Shri Navaratnam)