TOKYO, June 27 (Reuters) - Japan's Nikkei share average

fell 1% on Thursday, giving up most of its gains from the

previous session, as the yen's slide past the closely watched

160 per-dollar level put traders on high alert for intervention.

The Nikkei had dropped 1.05% to 39,248.88 by 0145

GMT, retaining just 75 points of Tuesday's rally.

Technology shares underperformed with a sell-off in U.S.

chipmaker Micron Technology ( MU ) in after-hours trading

souring the mood.

The broader Topix lost 0.49%, with a sub-index of

growth shares sliding 0.8%, compared with a 0.22%

decline for value shares.

Risk events loom for investors in all asset classes,

including a U.S. presidential debate later in the day, and the

release of the Federal Reserve's preferred inflation gauge on

Friday.

The yen was last at 160.44 per dollar, after

touching 160.88 overnight for the first time in 38 years. A

plunge to 160.245 in late April triggered official Japanese

currency intervention worth about 9.8 trillion yen ($61.08

billion).

The proximity to the quarter-end may also be influencing

markets. The Nikkei saw a three-day run of increasingly strong

advances, culminating in Wednesday's 1.26% surge.

"The size of yesterday's Nikkei gains were very surprising,

and I don't expect it's just me who thinks that," said Kazuo

Kamitani, an equity strategist at Nomura Securities, adding that

the large volume suggested it was the work of overseas funds or

securities dealers.

The technical test for the Nikkei now is whether it can

reclaim the May 20 high of 39,437 by the end of the week, he

said.

"If not, yesterday's rally will likely have been just an

anomaly," he added.

($1 = 160.4400 yen)

(Reporting by Kevin Buckland; Editing by Subhranshu Sahu)