* Higher equities hurt low-yielding yen * Net short positions in yen climb to 6-year high * Commodity currencies fall as oil prices slip on Iran deal * Aussie dollar under pressure on RBA intervention concerns By Jessica Mortimer LONDON, Nov 25 (Reuters) - The yen hit a six-month low against the dollar and a four-year trough versus the euro on Monday as a deal on Iran's nuclear programme sent shares higher, prompting investors to sell the low-yielding currency. The yen, which typically falls when share prices rise, has weakened recently on the belief that the Bank of Japan will implement the most aggressive monetary stimulus among major central banks. The dollar rose 0.5 percent to 101.73 yen, having hit 101.915 yen, its strongest since late May, as a deal between Iran and six world powers to curb Tehran's nuclear programme buoyed Asian and European shares and caused oil prices to drop. Positioning data last week showed currency speculators increased net short positions in the Japanese currency to the most in six years. "We are seeing equities continuing to perform strongly and the yen is being sold off as the funding currency of choice," said Jeremy Stretch, head of currency strategy at CIBC, adding the dollar could be heading towards 102.50 yen. Traders said some investors were reluctant to be short dollars before the U.S. Thanksgiving holiday on Thursday. Demand was also seen from Japanese importers, as Monday was a "gotobi" date, or a multiple of five, on which books are traditionally settled during a month. The euro rose as far as 137.98 yen, its highest since October 2009. It was last up 0.3 percent at 137.64 yen. "Stops were triggered in dollar/yen, which triggered stops in euro/yen," said Bart Wakabayashi, head of forex at State Street Global Markets in Tokyo. The euro fell 0.2 percent to $1.3530. It stayed above last week's low of $1.3399 hit after a media report suggested the European Central Bank could opt for negative deposit rates. This was later played down by the ECB. ECB Executive board member Benoit Coeure said in Tokyo that slowing price growth, or disinflation, would continue for now, but would not progress to deflation. Falling oil prices weighed on commodity-linked currencies, with the Canadian dollar dropping to a 4 1/2-month low of C$1.0584 per U.S. dollar. The U.S. currency was last up 0.3 percent at C$1.0549. The Australian dollar was down 0.2 percent at $0.9151, having hit a 2-1/2 month low of $0.9120, under selling pressure due to the threat of intervention by the Reserve Bank of Australia to stem the currency's recent gains.

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